I disagree on #5 the distance of the home worlds of scum that infest the Galaxy which rightfully belongs to my race alone.
Joking aside I would be perfectly okay if in the biggest Galaxy I did not meet an opponent for 5201 turns.
One option could be a slider that goes from zero to ten which sets the number of streams between races, may need bigger maps, I still think your maps are too small, and a second slider that activates if zero is chosen that sets the number of races that can be located in the "Home Sector".
Of course, I live to explore and expand, and I hate the AI pestering me every turn with deals that insult me.
This could be solved by an answer in diplo quoting the great W. C. Fields " Go away kid you bother me" or "If I want to talk to you, I'll pull your chain", results of which is it blocks communication with said race. At least for further trade talks, giving me the tribute that is my right as master of my empire could be an exception, but ignorantly trying to extort me should be blocked as well. this leaves only the fatally stupid decision to declare war which of course I would not want the suicidal AI from being denied.
Of course, you have players that want war, war, and more war, did I mention you have players that want war?
Small maps should be recommended for this style of play.
Other than #5 I have no problem with any of the others it seems they will kick-start your empires.
OT I wonder as motorcycles are built for whimps now days how many know where that term comes from. Just hope any who try's out a "74" doesn't forget the spark retarder.