You might also try a high-cut filter for the "off-stage" part (i.e., chop off some high end while the player's off-stage)... shouldn't be a problem to automate the changing roll-off amount. Just be sure to put the filter *before* the reverb in the dsp chain (so it's the direct sound that's changing as it enters the stage, not the stage itself!). As far as the verbs go, if you've got the CPU juice, I'd record all the convolution reverbs at the same time, then cross-fade between the files in the mix - this should keep everything happily in phase... "should". Although, this last point is kind of interesting, because I've heard opera recordings where they attempted to 'stage' the piece for the recording, and there's often a bit of phasing weirdness that happens when the performer passes from one mic field to another... it might actually be worth simulating (though that would be much trickier!). Depends what you want, I guess...
damn... now that I think about it, you'd actually have to automate the predelay as well, wouldn't you? Dietz, will MIR deal with moving sources? I can't imagine it, somehow, but I guess you never know...
J.