I seem to recall reading that there was a very different first draft of Stolen Earth/Journey's End. I can't remember if this was made up or if it was real. I don't think it was mentioned in the writers tale, so I'm going to lean into false, but if it is true then it sounds like the story would have been better.
The Brig would have been involved. He was to have returned in the Sontaran two parter and been a mentor to Martha (if true this would have been awesome.)
The Daleks would have been more extreme. There would have been Ogrons as servants, Vargas, Robomen (who would have been made up of other species they had conquered.) There also would have been Special Weapons Daleks, Spider Daleks from the comics etc. We'd also have gone into more detail into the worlds they had conquered, which would have included past planets in the series and cameos from other old races and monsters. Finally their invasion of earth would have been more extreme too. We'd have seen New York be completely destroyed and the after effects would have been shown in the episode with society having broken down in the streets of many cities, buildings in ruins, not enough doctors to treat the injured, no enough police left to manage the criminals etc. The Doctor wouldn't have parted with his companions in such a light way. Instead they would have told him that they had a lot of work to do and he would have understood.
There also was one scene in particular during the Dalek invasion where they killed the Prime Minister after making him publicly bow to them in front of the ruins of 10 Downing Street and declaring the Daleks as masters of earth. (A trace of this does appear to still be in the show, as we hear him and other governments signing over power to them on the radio, but rather than kill him we just hear ALL HAIL THE DALEKS.)
Rather than the Osterhagen Key Martha and the Brig would have used the teleporter technology to make their way to the Dalek ship where they would have worked with an alien that had escaped from the Daleks experiments to try and sabotage it. (There would have been other races in the reality bomb test, not just humans including Sontarans, one of whom's colony would have been captured.) Martha's husband Tom Milligan would also be working for UNIT and would have been exterminated in front of her during the Daleks invasion on UNIT HQ.
In the very first draft it looked like Rose wasn't returning, as Billie was busy, so she was absent apart from Turn Left, and Donna wasn't there either YAY. It was Penny instead. Penny would have been the main companion of series 4. She was to have been a love interest of the Doctor, with the two in a full relationship from early on in the series. This is the actress they hired to play her.
Honestly I wish they had done this now. I never used to, but that was when I was wanting New Who and Old Who to be the same thing. I don't anymore, so why not play to Tennant's strengths as a romantic, tragic hero and give him a proper love interest? Would have been better than Donna. Penny was sadly dropped after Catherine Tate expressed an interest in returning, though the actress and the character of Penny did appear in the first episode of series 4. You can tell the first episode has been somewhat rewritten as Penny still gets more involved in the action than you'd expect a guest character to, but unlike in the first draft where she joins him after being captured, in the finished episode she stomps off calling the Doctor a lunatic, whilst he comments she just doesn't have what it takes as an in joke. To think in another life she gave him wowzers in his trousers.
Anyway yeah Part 1 of the season 4 finale was going to have the Doctor and Penny visit the Shadow Proclamation which would have included, Krotons, Mondasian Cybermen (in the Revenge of the Cybermen design), Raston Warrior Robots, Sontarans, Autons, Krilltrane, Slitheen, adult Adipose the size of a house, Gelth and all manner of strange creatures. The Shadow Proclamation would have demanded that the Doctor lead them into war, which he would have refused, though it would have been treated a lot more seriously.
Midshipman Alonzo Frame who was also a guard there, would have helped the Doctor and Penny escape the Shadow Proclamation. The Brig, Martha, Jack and Sarah would have summoned them to earth just like the finished draft, with Harriet Jones dying. After the Doctor breaks his way into the Medusa Cascade, the Daleks would have attacked the TARDIS, shooting it out of the sky and sending it crashing into a Dalek infested London. Alonzo would have died saving the Doctor who would be shot anyway and cheat death the same way using his hand, leading to the same cliff hanger at the end of part 1. (Whilst Jack and Torchwood teamed up with Sarah and her gang to fight Daleks and Robomen before getting on board using the same way Sarah did.)
In the second part the TARDIS would have been thrown into the vat just like the finished version, but Penny would have gained Time Lord powers from touching the glass (NO Tennant double) and escaped. The others meanwhile, Brig/Martha Jack and Sarah's gangs would have tried to stop the Daleks by messing with their ship, but were captured, Penny would have then shown up in the TARDIS and stopped the bomb and freed the others, but before they could shut down the Daleks power, the Daleks would have overpowered them, until the Shadow Proclamation arrived, who would have rescued the Doctor and his army of companions.
The Doctor would then be forced to face up to his responsibilities and lead the Shadow proclamation's forces to launch a full scale attack on the Dalek mothership before they could repair the reality bomb. The Shadow Proclamation's forces would distract the Daleks whilst the Doctor and his companions snuck into the core of their ship, which Penny and the Doctor would have destroyed together, whilst his companions held the Daleks off. The Doctor would also have faced up to his responsibilities that he had to destroy the Daleks.
All the planets would have then been restored by the Proclamation after (NO towing the earth scene), but when the Doctor got back to earth Penny would have died from the Time Lord knowledge in her head, and the Doctor would have buried her near a monument to the Time War on the only planet that had survived the conflict. He would have declared her the last casualty of the time war.
Losing Penny, being forced to kill off the Daleks, and the millions dead on earth would convince the Doctor to travel alone again, leading to a darker arc for his next series.
Sadly however this draft was junked for many reasons.
First and foremost the budget. RTD didn't realise the struggling Beeb didn't have anything like the budget he needed for vast Dalek armies, Ogrons, Robomen, New York being destroyed, and the final war. Nicholas Courtney meanwhile was also apparently out of the country and so he wasn't able to reprise his role in the Sontaran adventure, and therefore there was no time to introduce him in the Dalek one. Tom Ellis and Russell Tovey were also unavailable. Billie Piper meanwhile did turn out to be available so obviously she was inserted into the story, which necessitated the need for Handy and more focus being put on her and the Doctor and them getting off with each other at the end. The lack of Shadow Proclamation saving the day also meant that there was no final battle, so the towing of the earth was added to be a big event instead. Donna replaced Penny as we've already been over, and RTD I guess changed his mind about killing the companion having grown fond of Donna and came up with the memory wipe, with the Osterhagen key being invented to give Martha something to do.
Personally though I think the first draft would have been cool. Just a shame it didn't work out. There's a good idea in Journey's End buried under all the silliness.
