I am not sure about precursor planets honestly. I am not really a fan of having super high value planets available early game myself.
Planet gen options for start are something we can look at. But the default continental layout for Terrans will likely remian.
Yea, the balance issue with someone finding a planet with +10 base Production on it or something early game is a really difficult issue. On the other hand, PPs could be a lot more special than they are. I'd imagine a happy compromise is to require them to be "explored" or "figured out" or "turned on all of the way".
There are probably some cool ideas there, but it seems like it's not urgent to come up with them all during the 1.0 scramble.
Special, but not OP, something that you're happy to find now, but grows with you. And something that someone else will want to take away from you. It's an interesting problem to think about.