Sounds like an interesting suggestion. You know that I've always been a big fan of AltiVerb, and I'm sure you could come up with a valid version. I doubt that you will be able to get the same blend between the instruments and the same sense of spaciousness, though. But yes - the music will be the same! ;-)
Apart from that, I would like to repeat that MIR is not just a reverb. It is the _way_ to a believable and good-sounding mix that is so much easier and intuitive than dealing with myriads of mixer channels, AUX-sends, indivdual plugins and so on. If you are a full-fledged technician, this may not be an issue for you. If you're a composer, arranger or any other type of "just a musician", you will be into music with MIR after a few moments, without leaving your very own domain.
PS: ... and if you're a technician, your results will surpass conventional virtual orchestral mixes with just a little practice, as the learing curve is very flat.
/Dietz - Vienna Symphonic Library