[Septimius Severus]

I like the concept of themes and more team games are very much needed.

Heat (fire & blood?) vs cold (water/air) could make for some very steamy action. One team might have cold resistant units, the other fire resistant units. It would be an interesting challenge to see fire vs. water go head-to-head. If your splitting the blood as a secondary theme for each team that might even things a bit. Using appropriately themed pretenders might also assist in protecting each sides unique advantages, that is if you want each side to have unique advantages. Once you've refined and crystalized the concept, I'd enjoy such a matchup. Love to observe it as well.