This is leading me away from Unity as a main tool, and making me look at MonoGame instead. MonoGame is at version 3 and right now supports the whole XNA API v4. This appeals as I can use my normal IDE, my .NET 4.5 (Unity is still on 2.0) and publish to my target devices easily. The downside is that I have more work to do as XNA is a framework - and a simple one at that. I think Unity has some use to me in that I can use it prototype still, but I think it'll end there... unless they release full Win8 ecosystem support on the next couple of weeks.
The paper design of the combat mechanic is going quite well. Hopefully when it's a bit more nailed down I can start sharing some of it. I'm working on a prototype to prove it out.