Well, the idea is good, though it's a bit challenging to setup. Although there are a lot of theme available for SMF I'm also using a certain number of mods, to add extra features... and making add mods working perfectly in multiple themes is easiest to say then to do...
Now I'm having an issue with the latest forum update, which seems a bit bugged. While the dev team is sorting out a couple of nasty bugs, I had to roll back to the 2.0.11 version...
But I'm putting this is my things to do list. I like the idea.