I just don't see why you think Osgood is so inextricably linked with Kate. We've had her before Osgood was around and we've had her in stories after.
They've done about 30 audio series, appeared in dozens of comics, books, video games and yes 4 episodes including the 50th, the most popular episode of the entire 2010s in terms of viewers around the world together, that's why. They are firmly established as a double act in the fans eyes and in universe where they are frequently shown to be best friends whose fathers knew each other. Sure now and again you can have one member of a double act appear on their own, but that's a lot different to replacing one.
Also Osgood is the daughter of a classic character too, establishing her link with UNIT's history. There is also a fan theory that her mother is Laird from Resurrection of the Daleks, which unlike all of their stupid retcons, like having the Brig be a Cyberman or be the Brigadier before he was Colonial Lethbridge Stewart, would be quite a nice link with Classic Who and establish why she likes the Doctor who avenged her mothers death and could give the Daleks some established history with a character and show the consequences of their actions etc.
Again to me this just comes over as RTD being an egomaniac. This red haired babe, will probably do NOTHING in this story that Osgood couldn't have done. She'll just be the scientific advisor the same way Osgood was. I very much doubt that she will have such an unbelievably different character right away, plus Osgood has a huge fanbase, the actress absolutely would come back, so there is no reason not to, but RTD is so petty with characters he doesn't like, he'll still replace Osgood anyway. Remember this is also the guy who created an expy of Adric, just so he could humiliate him and have the Doctor reject him. Who turned UNIT into fascists that capture and abuse women because he hated UNIT, and who had 5 million Cybermen get trounced by one Dalek because he felt the Cybermen weren't as good villains.
None of those things are what a professional does. Fans shouldn't have to worry if a writer hates a character, that their favourite will be absolutely trashed and undermined in the show, the viewers eyes, which in some cases can take decades to overcome. Again I absolutely will condemn Terrance Dicks over everything he did to the Cybermen. He came over 100 percent as a petty, ignorant, vindictive (as his dislike of the Cybermen was partly inspired by his own dislike of Kit Pedler, which was in turn motivated by snobbery as he felt Pedler had no business being a writer. Pedler got the last laugh however as he ironically had a bigger career as a writer outside of DW with Doomwatch) unprofessional hack in refusing to use them and then humiliating them in the Five Doctors. Someone should have pulled him aside and put him in his place there.
I've always said when it comes to adapting other people's creations you should always be a John Semper Jr, rather than a Sam Raimi. Now I do love Raimi's work normally, but when it came to Spider-Man he fumbled the bag badly for the third film. Both Raimi and Semper were pretty much in the same position. They were both fans of the 60s and 70s eras of Spidey, and both given what at that point was the most mainstream Spider-Man adaptation to produce. (The 90s animated series in Sempers case, the films in Raimi's.)
Now at first both wanted to recreate the stories from their childhoods, but both were told to include Venom and Carnage, hugely popular 90s characters that neither was familiar with. Semper Jr, did his job as a professional. He researched Venom's character and approached it as a writer and tried to see what he could get out of Venom and Carnage that he couldn't with other characters, not as a stupid fanboy, with fanboy prejudices wanting to recreate his childhood. As a result his adaptations of Venom and Carnage were universally beloved. They not only heightened both characters reputations, but they were faithful, and introduced new and compelling aspects to their characters which have popped up in every single adaptation since! He even created the Spider-Verse, a multi million dollar franchise through his version of Carnage and ironically an adaptation of one of the most reviled comics, the Clone Saga. That truly is getting ice cream out of shit LOL, the roots of an Oscar winning movie like Into the Spider-verse began in Sempers version of the Clone Saga a story so bad it almost bankrupted Marvel.
Meanwhile Raimi was..... a petty, spoiled, tantrum throwing fanboy when told he had to include Venom. As it was deviating from his vision, he basically half arsed it. He didn't do any research for the character (he didn't even know what symbiote meant when someone asked him at a convention.) He made Venom a minor character in the movie, with virtually no backstory, left out all the nuances of his character, all the things that made him interesting, and then when Venom wasn't well received had the cheek to say it was the studios fault for making him include Venom and that was proof the character wasn't interesting.
The sad irony is that Venom and Carnage are a perfect fit for Sam Raimi's style! Ironically more so than any other villain. He had to change Doc Ock, unknowingly to be more like Venom, then there is Raimi's background as a horror director, with Venom and Carnage both essentially being horror movie villains. Are you really telling me a horror director couldn't have done something with scenes like this?
If he'd done just an iota of research he could have done a brilliant version of Venom. It could have combined all his favourite things, superheroes, demonic possession, horror movies into one! Fact is he was an unprofessional fanboy hack in that instance, who HATED having to compromise HIS version of Spider-Man. It pisses me off the way fans still defend him for that, as though the studio was so unreasonable for asking him to include Venom. Fact is Sam, you were making what at that point was an abridged version of the Spider-Man story for mainstream audiences. Venom is a HUGE part of that, he is one of Spidey's archenemies. It is not unreasonable for the studio to say "make him the main villain for the third film over the f*cking Sandman a minor villain who was nothing more than a gimmicky character". It's not your f*cking character, when doing someone else's character you have to accept that sometimes your vision will be compromised.
PS the same applies to Bob Holmes as well. He was EXACTLY like Raimi when it came to the Cybermen. He was an unprofessional, in that case snob who thought arrogantly that all returning villains were a bad idea, that was only done to appease the stupid kiddies. Therefore like Raimi he half arsed it when it came to writing Revenge of the Cybermen. He didn't even attempt to write the Cybermen in character and when the story wasn't well received arrogantly said that was proof that they weren't good villains. Again much like Raimi, if Holmes had bothered to do one iota of research, he would have seen that they were a perfect fit for his style! The Cybermen combine all of his favourite tropes. They are villains who were once powerful, who have fallen on hard times and are trying to regain that power, they feature elements of body horror, they embody horror movie tropes, like vampires they turn people into members of their own kind, like Frankenstein they are a science gone wrong, mish mash of different things, and Tomb of the Cybermen is basically a prototype of the entire Hinchcliff era being a Hammer horror, in this case a Mummy movie in space!
The only area they don't work with him is that he couldn't do the flowery dialogue, but even then the Cybermen often worked with a slimy, treacherous human like Tobais Vaughn and Cleeg who could have fulfilled that role.
Finally same applies to Moffat too. His dislike of the Master is why we got Missy. He similarly HATED that character, and was forced to include him, and basically thought "f*ck it the Master is only liked by sad anoraks who want him back to recapture their childhood, so they won't notice if he's completely different, I will just do my usual River Song character again." Again much like Holmes and Raimi he might have actually been able to do a good version of the Master if he'd tried, as his version of the Great Intelligence is basically the Master. Certainly Richard E Grant is a great choice for the Master, his costume, his dynamic with the Doctor of being so utterly obsessed with destroying him. Those all fit the Master rather than the Intelligence, who was a cold logical villain with no grudge against the Doctor.
In all instances these writers botching the villains returns, big breaks, botched their reputations and stories for years, decades after. Thanks to Holmes the Cybermen's comeback in the 70s didn't go as well as the Daleks or even the Ice Warriors, so they fell out of the publics perception for that generation. Had Saward not done Earthshock, it's easy to see how they could have ended up just being another 60s badguy. Meanwhile Five Doctors began a process wherein they became punching backs in 80s and even new who too.
Raimi meanwhile botched Venom's chance to go mainstream like the other Spidey villains, and indeed he also robbed us of a chance to see the black suit saga done justice as thanks to the copyright bullshit and shared universes, chances are we'll never see it.
Finally well, I don't have to tell you the shit that has happened to the Master as a result of Missy? From me getting banned from TV Tropes for simply writing in the FACTS. Not even an attack on Missy, just the FACTS about his character, to Big Finish having the burned Master be jealous over River Song being married to him! To fans saying the guy who wrote the Five Doctors didn't know the Masters character as well as Moffat because he didn't have them as friends (that would be Terrance Dicks the co-creator and overseer of the entire Delgado era?) It will be a task of Herculian proportion just to write the Master as the Master again without being accused of being homophobic or sexist!
Now getting back on topic LOL, obviously Osgood isn't as big or important a character as these guys, but still you can see how overall the attitude of "I can do what I want, I run the show now, if I don't like a character, bye bye" is a terrible attitude to have to making an old established series. Yes you can write out characters, but you have to make sure it is done respectfully and for a good reason too. Ultimately RTD is not doing that with Osgood, and indeed her future in the audios could even be in jeapordy as RTD will presumably want his new sidekick to accompany Kate too.
It's a huge dick move on his part.
Again though I don't want to put anything on the red haired babe, as I HATE it when people are c*nts to the replacement of their favorites. As we've been over poor Katie Waissel's entire life was ruined because of that. (Though obviously it would never be the same as DW isn't as popular as X-Factor, Osgood whilst popular with some fans isn't exactly a household name LOL, and hopefully the world has changed for the better since then, but still I just want to make it clear that's NOT what I'd do.)
I think the real question is, Maxil what do you think of the red haired babe LOL. I mean I reckon he likes her because she is a woman, but just to be sure. I think she's gorgeous, but then again she is my type I'd say with her big nose and is obviously a dork too.