I've kind of got that. I've a set of 700C sexeh carbon road wheels and 3x650B wheels (rear, front, front dynamo). I thought I might ride it this weekend but my cassette hasn't turned up and I don't wanna run old cassette new chain.
I'm trying "not racing" - cheaper and I always win.
I've got the two sets of wheels for mine almost ready now... oh except one is missing rotors and the other is missing a cassette and sealant. :)
It's ok, I'll probably just ride the MTB.