I don't know that it necessarily needs a whole lot of complexity, but it needs less abstraction. Being very abstract works really well when the primary conflicts are not between players, since you are telling a story. However, in Jupiter Sovereign players can be incredibly powerful, and part of the reason why we don't care about any realistic simulation rules are that we care about the end rather than the means: your psion who can disintegrate things with his mind is definitely going to destroy that door, but it's a question of whether it'll cause backlash or corrupt him that matters.

I actually was working on a game system for a wargame back when I was working on a setting called Legacy of Eight (as many of my other settings seem to be, it was a transhuman science fantasy setting), which was intended to have a rule-set that supported interoperability between a wargame, tactical boardgame (picture the DOOM boardgame), and roleplaying game. It was not really ever something that came to fruition, but it could actually be interesting. At the very least it involved brainstorming some tactical ideas.