I'm not sure WTF is happening here, but I think I actually side with Lecic on this one...
Here's an idea: just implement and refine Empire mechanics into the game and let players sort it out. If you want a combat heavy playstyle join a faction war PvP server, if you want a more peaceful experience join a PVE server where combat only happens on joint decision. This is not a new concept, it exists for any MP open world game already - You don't typically have creative builders or logic heads playing on a faction war server, and if they joined one thinking they should still be able to play that way without getting constantly destroyed and hassled, they are not in store for a good experience
As a sandbox game, I don't think that either SP empires or MP Empires should have any artificial limitations or benefits. It seems obvious that if all other variables are equal (individual time played, skill level, etc) having more people investing more time and resources for a shared goal should make MP Empires more powerful than Solo ones.
Personally I mostly play Single Player because I don't have the time investment required to be competitive on a large scale, but if I were able to play competitively on an already established server I would expect to start as an underdog lone player and slowly build my empire either through AI fleets, or joining other like-minded players. I'd be too small for larger empires to notice until I either amassed a decent stockpile of resources or pissed somebody off, then I'd have to use tactics, alliances, and a good deal of luck to survive until I was big enough to stabilize my position, at which point I would now either be one of the larger empires that new players either had to cooperate with, avoid, or slowly build up to compete with, or allied with one - Or perhaps in a group of smaller empires that work together to keep larger empires in check. If I constantly got beaten down before I could ever even get close to a decent level I'd probably move on to a more balanced server, unless I specifically joined a cut-throat server for the difficulty challenge where dying and losing everything is just part of the fun