I do the same thing, if I understand your response correctly. My electrostatics ( Soundlab U1 ) serve as my stereo system, and also as right and left front in the surround system.
As long as you have individual adjustments for each speaker ( your processor should provide ), you can mix Maggies with cone side, rear and sub speakers and achieve good results. I am suggesting this, assuming that the priority in your life is in having a great stereo system, and occasionally listen to the surround. I have four brands of speakers in my own surround sound system, and they integrate well enough for every visitor to comment about the wonderful sound.
If cost were no object, and you could build two totally separate systems, one for stereo and one for surround, in two dedicated rooms, I have no doubt that the surround could be made better by closely matching the components. At a site such as Audiogon, many of us emphasize two channel music over surround, and my comments clearly come from that camp. My stereo is the highest priority, and having my large front speakers do double duty, is the only way I can have both formats. Obviously if I have to sacrifice quality, it is in the surround. That being said, I doubt there are a lot of surround systems that have better quality front speakers than Maggies or Soundlab, I think your plan is workable.
