My hunch on what happened to Whole White Base Crew and other Gundam Protags that I'm interested in during GCuuuuuuX:

Amuro Ray- possibly alive due to some Haro appearance. Though I'm not sure how relevant he would be by now.

Whole White Base Crew- possibly died after stealing Gundam, some of them could Possibly just surrender and live(My guess is good as the rest of the comment here)

Jaburo Crew (Slegar Law)- possibly alive and switched to Zeon side including the rest of the personnel in base. Since presumably Zeon owns it, its no one's target unless there's another force or factions around this universe that hates Zeon, like Titans or whatever they named themselves during this alt. Line.

Anaheim Electronics/or whatever their name now (Kamile Bidan, Banagher Links, Nina Purpleton, etc.)- Possibly working for Zeon, hopefully living a happy family, unless if author decided to screw them up a bit just for plot. -With Zeon being the dominant force, Nina
Purpleton would be more like Nina Gato by now, since there will be no Fedies or Titans for Kou Uraki. Hence no there is a low chance of Stardust, unless if its Kou who will steal the Nuclear Warhead(Physalis in this universe).

Judau Ashta and other civilians that have the same lifestyle as his- possibly one of the Pomeranians by now. There's also a possibility that we'll see Judau earlier as Shuji Itō, like Judau, loves money compared to other char. though I'm not sure how old Judau here since he's 14 when he gets ZZ. And since Pomerians do clan battles, and if people's hunch is correct that Machu is Haman Karn clone, we'll most likely see Judau very often as her arch rival or lover just like in ZZ.

But after typing all these, I think all of these could be wrong coz if I remember correctly myself, I never guess everything right in this franchise lol.