The problem is its boardgame roots. With each update there will be more and more units to move around. Reducing the NPC's won't help as within a turn, everyone will have produced as many units as the npcs were anyway.
3 cradles increases things considerably too.. but for obvious reasons i don't want you to close two of the cradles!
~20 players.. makes it hard too. I know you are a very friendly mod, but locking signups and making it a bit easier for people to kill each off will make the game a lot easier to run.. about 12 players would be optimum imo.
can't think of much else.. problem of success.
an OY! edit your post that says i lied!!!