so if one alliance, lets use Asc for example, should be going fully random. They end up in those so called random galaxies. Where they can mass recruit in those galaxies - out of tag/support planets if needed - because out of tag planets, none alliance planets, can defend others iirc - you are saying that private mixed gals are stronger?
This is just one example on how to turn your idea around. Im not saying it is a bad idea, there's just so many holes in planetarion and it's current setup that any change on private, random or mixed galaxy setup does not work. This is because PA adds crap to the game every round and does not have a layed out plan about where to start from and where to go to. They add things on the fly, important things by that because players request it. And then 2 rounds later that player quit the game and the rest of pa is stuck with those addons for many many many rounds.
I love the fact you are coming up with idea's, please do not get me wrong. But plan for long term. And make sure the plan is bullet proof.
Give it a few more thoughts, as imo you are on the right path to solve an issue PA is having right now.