I posted something in response to your other comment...have you looked into Capture One? They have a free trial, you should give it a shot and see if it will work for you.Also depends on the lense he owns, doesn't it?
Depending on how big your studio is, stepping down to an aps-c sensor could be a pain as it will make your lenses not appear as wide. Might be worth it to consider a newer 1D, or a 5D mkII, or even an old 1DS (if any of those work). It might make your studio feel less cramped if you are tight on room. In one of the smaller studios I worked in, I hated shooting the 20D but loved shooting the 5D. Would have not been as big of a deal in a bigger studio. Just something to consider