[quote=@vancexentan]
Will we all be forced to be piloting Gm's, or Jegans? What exact time are we piloting these things? Zeon Remnants can be anything from the post one year war to Neo Zeon to the Sleeves
[/quote]

No, you won't be forced to pilot GM's or Jegans. It'll be a selection of various variant versions of those, and some mass-production Gundams and other suits. I haven't nailed down the specifics yet, but there'll be a healthy selection. Part of the units' background will be that they're also operational test/evaluation for previous models of mobile suit and putting them into action, and their mecha were pulled together from the remnants and left-overs from earlier conflicts and special groups that have since disbanded.  
As I said in the opening post, I'm not going to be fretting too much over exact continuity, but for the sake of answering your question, post-Char's Counterattack but pre-Unicorn, or even alongside Unicorn, but removed from the Earth Sphere and more out in the asteroid belt/Mars/potentially even the Jovian system, leaving things free to not be too bothered by the same characters, events, etc. I will be deliberately ignoring any manga, side-stories, etc that happen in those places and times to tell my/our own story, and the same for post-CCA/UC100 continuity. 
Also it will be a group of Zeon remnants generally smooshed together, consolidating under one group for survival etc and otherwise being a nuisance in the outer Solar System.