I don't understand what you're asking.  It's already possible to have multi-star maps.  It sounds like what you might be asking for are maps with numerous stars with just a couple planets around them.  If you really want maps like that, you can design them yourself using Galaxy Forge or even the Map Designer.  It's also possible that other people have made maps like that that you might be able to download.

The general consensus, at least among players who play against other people online over Ironclad Online (what you might call "serious Sins players"), seems to be that multistar maps just don't make for very good games.  IMHO, it works out best with a map like Gateway where the players start on one star but another star or two is available for further economic expansion.  I've made a couple custom maps like that (with an extra star or two); I just wish I could get people to give them a try.

Yeah.  I wish I could get them all to use the Sins Optimization Mod and to learn to play custom maps.

You know, that sounds like an interesting idea--what if you had multiple planets that could be owned and conquered individually within a single gravity well?  You would be able to place structures around the planets the same way you do now but they'd be limited to the same orbital radius.  That sounds very interesting.  I wonder if anyone could possibly mod something like that.  I would assume that it's hard coded and can't be modded.  I suppose that culture could radiate out from planets based on the distance from the planet.

Perhaps in a Sins-2 there could be an option for a game type like that.