This is my first suggestion, please don't ridicule me into oblivion.
This game has a feature that caught my attention right away- Terrain bonuses. I have not played a game that had these bonuses as significantly as Illyriad, and I most likley never will. Although these bonuses are intricate and accurately reflect real life (up to the fantasy elements of the game), I feel something is missing- Race specific terrain bonuses. In other words, bonuses that affect a specific race, or even a spefic unit in that race, on a certain type of terrain.
Take, for instance, the elven trueshot. The description on the "races" section of the home page states that "(elven trueshots) kill with perfectly placed headshots from hundreds of yards away - even in forests." This indicates that the elven truechot is more proficient than other bowmen in forests, which to my knowledge is untrue. Elven trueshots, however, could be made to be this way, thus accurately matching the discription on the homepage, as well as the descriptions given in many fantasy novels.
Another thing I have noted is that no race is more or less proficient at killing another race than any of the others. Taking another quote from the elven trueshot, "Many times, Orcish intruders in Elf-held forests die without ever seeing their enemy." Are orcs bad at attacking elves? Not yet, but with a tweak, this could become reality, adding another devious element to the already highly strategic and engaging game of Illyriad.
Pros:
:The game would more accuratley reflect the homepage, and many fantasy novels
Various races wouldn't be at a disadvantage in their starting terrain (elves, dwarves).
Attackers and defenders would have even more strategies to consider before sending away an army.
Cons:
GM Thunderkitty would be up to his kneck in tedious programming. 