1] Yea adding races is cool and all, but how about making costume races? You can do it like making a hero, where you can select from a list and have X amount of points to spend. As well as being able to edit [but not limited to] height/weight/ear shape/skin [ie scales/hairy]
2] Kinda stealing this one from Master of Magic, but it would be cool to be able to create customized items made from magic. Cost can be mana + crystals + time and will depend on item type and what magic effects it has. IE two handed weapons get 6 points of customization [selected from a list] while one handed swords get 3. Enable users to name the items and what it looks like [select-able from pre-made skins]
3] Better diplomacy options. Like trading/offering: city's, spells, units. Even create a spell that makes agreements binding.
4] I would like to see randomized maps as well.