/equipset [spec:1] Frost; [spec:2] Blood
/usetalents [spec:1] 2; [spec:2] 1
Since the talent is a 5 second cast, there really isn't a way to wait til the cast is over to cast your presence. You might be able to write a mod that does it, but I don't think you can do it via simple macro.
If you use power auras though, you can make an aura for when you don't have any presence at all, I believe. I know I made something like that for my paladin when I would forget and leave crusader aura on for parties.