The screen shot below is from a recently completed South America game. The player in question didn't win but it was a near thing... three of us were able to make a coalition and hold him and take the rest of the map. I've been around a long time and defensive tactics stalled him long enough.
My point... 8 heroes??? 2x 5 star, 2x 4 star, and 4x 2 star. How can that possibly be fair? In general my guess all you will do is demoralise any new players and discourage them from continuing to play the game.
I don't have an issue with adding heroes as a feature but no one should be able to field that many. For players with none (or 1 or 2) they will find it very difficult to compete. My suggestion would be to limit the number of heroes that can be on a map at any one time. Perhaps base it on the same number of people that can be in a coalition. So if coalitions can have a maximum of 3 players then any given player can only field 3 heroes at once.
MorkOfOrk
Na-nu Na-nu