Sounds interesting, I'm always up to hear good ideas.
For me the Imperium is just a backdrop for adventures, though I'm just making up a lot of this as I go along. For example here is a fresh Marine Lieutentant I just pchopped:
I call him Lieutenant Albert Kodolitz, most likely the son of a noble ready to take his place in an Imperial Regiment such as the 2359th Imperial Dragoons "Knight's Equinox":
Which are battle dress Marines, I usually say that Marines are the standing arm mostly as they travel between worlds, unlike planetary armies which are more like reserves. The different uniforms of the various planetary militaries works well, for many old turn of the 20th century forces in europe had regiment defined by their uniforms so with the Imperium, there is a sort of return to this way of doing things. To me the Imperium is rather stagnant and it is this class stratified, inner core that drives people out into the frontiers like the Spinward Marches looking for opportunity and a better life. Even the seconds sons of nobles would head away from the core, in hopes of carving out a better life or fiefdom or so, they may not make the best officers (and alot of officers are not nobles) but if nothing else they die bravely for the Imperium and make exquisite corpses, or maybe not, maybe just Lord Carddigans who get shot by their own troops.
I like the Solomani, now they have no nobility, and I usually have there be a tension between factions in the solomani sphere with the Condfederalists on one side vs a newer "Republican" faction which favors both irredentism of their lost worlds and a stronger central government.
Though the current adventure I'm making is called the Ice Queen and involves a group of adventurers resucuing a "Blue Darrian" Princess and escaping Sword Worlds and Zhodani forces in the Entrope worlds during the Fith Frontier War. Maybe a good chance to throw in a BD equiped character and show when BD is good and when it is bad. Cutlass skill might come in handy too after the ammo runs out.