I'm afraid that this is not possible at all, the only ways are these which are stated above i'm afraid, if you don't have enough room for other contacts, you could possibly use:
MessengerDiscover; this will allow you have more than 150 contacts if that will help at all, but I must warn you that this conflicts with StuffPlug if you have them both installed, and it may not allow messenger to start, but it depends what features you use for both.
