I am playing Clash of Clans with two profiles on the same iPhone device! I use my original apple ID when purchasing music, apps etc. I created a new apple ID for use only in gamecenter, because i bought a new iPhone and could not transfer my old game, as I had already started a new game on my new iPhone with my original apple ID. I then got hold of my old iPhone, created a new game center profile, "saved" the game with my new game center profile - logged in with this new profile on my new iPhone, and continued with my old game - this works.... BUT not 100%! Sometimes the phone automatically reloads the old game center profile, and I have to go to settings and log out, then log in with the new profile, and I am back online! This is not ofcourse not the best solution, however a solution...
I hope that this might help some...