A ceasefire won't help anything, it'll just move the goal posts. For any set of rules the game runs by, people are going to analyse them to try and gain an advantage on the opponent.
Take the ceasefire for example: I take it this applies only to other players, and not the independent planets you want to take over at the start? Well in that case, I'm gonna come and take planets near you before I take them near me. Then I'm going to work back toward my home. You aren't allowed to take them off me, are you, because of the ceasefire? In fact, are you even allowed in my systems? That seems unfair if you are, since you can scout me out freely, which is something no power wants a soon-to-be opponent to be capable of. So I just walled you into a tiny box, and by the time the ceasefire ends I'm gonna have a much better eco, and therefor fleet, than you.
And then you say: well, how about you are only allowed to expand to neighbouring planets? And you've restricted the available options yet again, and I'm gonna go away and find the next thing that I can take advantage of, again, and then you're gonna ban that too... Never mind that even if we just played the ceasefire head-up, with me taking my planets and you taking yours then I'm still gonna have a bigger fleet than you when the ceasefire ends because my build order is better than yours (that, after all, is what rushing is: getting a better fleet than your opponent, quicker). I'm casting myself as the competitive player here, not suggesting I'm leet or anything. I'll leave that to HunterX