I like the idea of armies in the deserts advancing along water routes. For that matter, you could have something similar for the European climates, like a "mountain pass" or "canyon" battle map. Kind of the opposite of a river map, where you've got two chunks of land and an impassable barrier in-between (save for the bridge)... These other maps would be two chunks of impassible land, with a ribbon of passible in-between.

This actually brings up another subject, where perhaps a general with greater stars (due to their greater experience) would start a battle in the better of positions. So ~ for example ~ if two generals fought each other in Switzerland or Tyrol, if one general is far more advanced, the battle map would be a tight constricted valley, with the more advanced general on either side of the cliffs. If one general was only slightly more advanced, perhaps the tight valley would become a broader one, with more access to the higher points.... and if there was parity between the generals, both would start on some form of a broad mountainous plain.

It's funny, but the more advanced TW has become, the less exciting I've thought the battle maps have been (with STW being the best).

Cliffs: Despite their presence, I've never felt they played that big of a role. Archers can't adequately shoot down from them (and from such height they should be twice as lethal or more), and any army trying to move around them automatically spreads out into this long line... IMO, make the height advantage more effective, the time to exhaustion on attackers more prevalent, and the AI's pathfinding more realistic.

Back to the idea of empire vs kingdom: As an empire, you're kind of all inclusive ~ there are many cultures and many peoples within your realm. They may or may not like it, but for the most part they accept it as they are semi-autonomous anyway. There is alot of scheming as to who will rule, and periodically rogue elements try to break away. Also, there's probably more graft and corruption. Still, you can grab alot of territory as an empire. As a kingdom, you are instead the predecessor to a nation. Your people are more or less homogenous. Their beliefs are more or less homogenous, as is their culture. I guess that, to me, the benefit to a kingdom is that you have less civil unrest from your home territories, but more from recently conquered territories, which would make it more difficult (and more expensive) to expand. However, beyond a certain point, assimilating new peoples might not be an economically viable option, therefore the kingdom becomes an empire. Once you're an empire, the people kind of settle down, and rebellions over population discontent are fewer, while rebellions from ambitious political / military figureheads are greater. Available money is slightly less, due to the burden of bureacracy (slightly lower production), but at the same time it's not entirely necessary to further train priests, teachers, etc.... Still, you would then (and only then) have the option of training some truly advanced units, pulling from all corners of the empire to create grand (and expensive) super units.

Yeah, and by the way, that would be an awesome idea for the military academy.... the ability of a player to create one (and only one) super unit... or to pick from a pre-made list: The english could have a "Yeoman's Guard", longbowmen that could shoot 20% further, and 20% faster. The germans could have "Royal Knights Templar" (as fast as Chivalric Knights, but with the Offensive / Defensive power of Gothic Knights)... whatever, just ideas. You could pick it, tweak it, make it, but you'd still have to make it, and you could only make it in the province with the military academy.