If fly gets ever introduced in this game a race of flying humanoids would be great.

They should be fast but not too much.

They shouldn't be able to wear an armor or not be able to fly if they do.

The negative bonuses should be introduced because they would be very powerful (for avoiding forest and mountain negative bonuses)

The problem is that whatever negative bonus they had, by using them one would still be able to recruit Sions Darklings and such, therefore having also a regular force of ground units.

The idea comes from an old but great Italian wargame called "Zargo's Lords"

they also had a race of dragons humanoids (already there), a Race of "Monks" very very weak but with great stalking skills (their main units would be invisible when moving) - I believe the expansion also hada race of sea creatures (would be great to have them, with underwater cities... but if the developers are interested maybe we could try to find the manual for the expansion on the net, to see how the sea people wee dealt with)