Mirage MCsi for surrounds?

My system has M7si mains + MC-2 Center and I love them. I have been looking locally for quite some time for either another pair of M7si or a pair of M3si which would become the mains, rotating the m7's to the rear. Getting tired of waiting, and shipping is an issue with both cost and potential damage, so fairly committed to local.

Had a thought recently of using MCsi as surrounds (currently early Paradigms). Have seen several available at very reasonable $, and shipping is much less a concern. Your thoughts?

Let me ask this another way... In general, is there any reason a center channel speaker(s) makes a bad choice for surrounds?
in general, rear speakers (esp. bipole/dipole types) are designed to project sound as broadly as possible, the idea being that you're surrounded by sound effects. front and center are typically designed to be more narrowly focused; in the case of a center channel you'd expect the sound to project from the middle of the action. ergo, in the usual case a well-designed dedicated rear speaker would be preferable for rear surround. however, mirages have an atypically broad soundstage--they're very room filling and non-directional, so i'd expect a mirage center would serve just fine as a rear surround.