Let’s take a look at how Gundam Unit 04’s story was adapted into videogame (and later manga) form.
The Redesign
In order to make Unit 04 suitable for rendering in videogame form, Hajime Katoki was tasked with redesigning the mobile suit. In addition to adding his usual Katoki-esque tweaks to its proportions, the main thing he did was simplify the overall look. It doesn’t have nearly as much surface detail as the M-MSV version, but it’s also not completely devoid of it either. Most importantly, it still manages to be immediately recognizable as Unit 04, which is no small feat.
The other thing he did is tease out some of the surface detail by giving it two different modes. There’s the “standard” mode, and the “boost pack” mode where it’s outfitted with additional armor and propellant tanks. This is a shrewd move that allows it to preserve more of that original essence in a practical way.
Ultimately, what we go from is this in M-MSV:
To this redesign (in standard mode):
And this Boost Pack mode:
This is how Unit 04 has been depicted in all appearances ever since, and it’s what the Master Grade model is based on, so it’s what I’ll be referring to going forward.
About Encounters in Space
In 2001, Bandai put out a PS2 game named Journey to Jaburo. It allowed you to play through the events of the first two Gundam movie adaptations.
As for the events third film, Encounters in Space, they left that to the 2003 sequel game of the same name.
But since this sequel only had one movie’s worth of content to cover, they needed to add some extra content to pad the game out. One of those is a mode called “Thoroughbred Mode”. This is a short little campaign that is, essentially, an extended and updated retelling of how Unit 04 and Unit 05 were deployed during the One Year War. It’s different than the story we saw in M-MSV, but that original story is clearly the foundation upon which this new one was built.
The Cast
The game’s story re-establishes the identities of the two Gundam pilots. Unit 05 is piloted by Ford Romfellow, a young hotshot with a penchant for risk. Meanwhile Unit 04 is used by Luce Cassel, who in typical anime fashion is the “Grizzled veteran who looks and acts like he’s in his 40’s, but is only 30”:
The characterizations here are the same as in the short story from M-MSV, but now we also get to see their appearance as well.
The Catch
The way the game is structured, you only ever get to play as Unit 05 in the Thoroughbred campaign, with Unit 04 always being your CPU-controlled partner. However, under the right conditions, you can unlock Unit 04 to use in one of the games other, non-story versus modes.
The Story
In this version of the story, Units 04 and 05 were not stuck being upgraded until the Battle of A Baoa Qu. Rather, they were ready to go right after the Battle of Jaburo. They were assigned to the Thoroughbred, a Pegasus-class sister ship to the White Base, which then launched at the same time as White Base out into space.
Their assignment was to go and check out what Zeon was up to at Granada, while also guarding the rear of the Feddie fleet as it makes its advance.
After doing a couple of simple missions, the crew discover a small fleet moving from Granda to A Baoa Qu to serve as reinforcements, and this is where shit gets real. The fleet is too large for the Thoroughbred to take on all alone, so Luce proposes that they let him go out with the Mega Beam Launcher, despite the fact that it was abandoned (and thus not properly tested) during its development phase.
Technically speaking, the subsequent in-game mission has two different endings which lead to two different story paths. However, apparently the mission is deliberately designed to make it extremely difficult to obtain the “good” ending, thus forcing you down the “bad” (and, to my understanding, the canonical) one.
In the bad end, Ford buys enough time for Luce to fire the cannon, which devastates the enemy fleet:
However, firing the gun causes its power generator to explode, which ultimately kills Luce:
That, my friends, is the true and tragic ending to Gundam Unit 04. After that, the rest of the campaign has Ford fighting alone to help prevent the peace treaty between Zeon and the Federation from being sabotaged.
However, if by some miracle you get the good ending, Luce survives, and the pair both get outfitted with the Boost Mode equipment. From there on the story plays out similarly to the M-MSV short story, in which they go to A Baoa Qu to participate in the final battle, and even get to fight the Bigro Kai (though this time neither dies).
So there you have it. That’s the expanded, branching story of Units 04 and 05.
Manga Adaptation
A year or two later the game story was adapted into a manga named Space, to the End of a Flash
I’m assuming it fleshes out the story even further, though I’m not sure if it still ends in the same way, or if it continues on with additional adventures. I’m pretty sure I read somewhere that at some point they drew both ending paths, so that’s something.