robbie williams is much better than he gets credit for. A lot of his songs are rocky and karma killer is a great song, but i cant see muse doing a cover of it
or, for that matter, of any other song. Muse may have done covers in the past (all of them brilliant, especially can't take my eyes of you, great version), but that was just before they got going
they dont need them anymore, and i think they would rather not