I worry about having too many Demigods because it dilutes the impact of each one (in GalCiv we kept adding races and people stopped really having a "favorite").
I think this was caused by not having much of a history for each race, and races appearing too similiar. Races played too much like each other, too. Planets built mostly the same way, and combat was almost always who had the bigger ship.
Galciv3 should improve it a lot though, hopefully they add in weapon ranges and rate of fire. Populations for races that differer (some like war, others hate trading with anyone, ect).
The level editor will probably be released for this game sooner or later - from what I hear beta1 had a functioning one but was removed.
As for heroes - 14 would probably make a better number. 3 new heroes for each side, rather than 2.
4 demigods, than concentrate on improving abilities of the released. After a while release the last 2.