Multiple star systems in a game. How can it work?

Lets se, why would you want that: Lets say were playing with multiple star systems and a 40+ player game (if they implement those huge games in this way), and you want to invade a star system were the enemy has allredy been fighting and building for a couple or hours.

Why ohh why would you want to bring a small army (at high cost btw, so you cant just "funnel" everything) with you instead of starting from nothing when the enemy has a fully functional base and army allredy? :roll:

Even if its the singleplayer galaxy map, why do you assume that the npc enemy and you will start every battle with nothing? Its not impossible for every game to start with nothing, offcourse. They could add some kind of level up mechanic or meta tech game or even some sort of story, so that you get some sense of progress between missions even when you start with nothing, but we havent heard anything like that so why do you automaticly assume so?