One of the advantages of mod making is you dont have to appeal to the mass community. Make the mod you like, and some will love it, some won't. But thats okay, if the idea doesn't appeal to them they wont download it.
But lets consider the mechanics (keep in mind this is coming from a guy that has never played any of the pokeman games).
1. Pokemon. Different ones could be applied as animals (less aggresive) or barbarian (more aggresive). These could represent the wild pokemon in the world.
2. Capturing pokemon. In FfH we allow units to learn spells on levelup, in this mod the summons would be learned upon successful completetion of a battle.
3. Summoning. Check out FfH for some of the ways we use summons, it should cover the basics.
4. Leveling up your pokemon. There are a few ways this can be done, xp can be given when a pokemen wins a battle, the summoner could choose what pokemon to upgrade when he levels, etc etc.
5. Defensive summons. This would be the SDK change. You would need a popup on attack so the defender could select what pokemon he wants to defend with. The AI would have to be trained on how to pick an appropriate pokemon.
These are base mechanics, completely outside the "flavor" of pokemon (I prefer to design without flavor). The question is, would a mod that had these mechanics be enjoyable? I think it definitly could be.
Whether or not you decide to use pokemon as the flavor or not I think the mechanics I outlined above (or whatever mechanics oyu choose) would make for a very interesting mod. The ability to capture summons, level them up and choose them on attacks and defends (with them having various pros and cons against each other) would be fun and a significant difference from vanilla civ.
Just my 2 cents, good luck to you.
