Any reason not to do this?

Brother your luck sounds like mine! It sounds like the guy cut the axle not the housing correct? I personally would fix what I had. Get the issue at hand fixed. For your car there really isn't anything to be gained by narrowing the rear housing without a mini tub/spring relocate that a different set of wheels with the proper backspace wouldn't accomplish. Then that leads to figuring out proper backspace etc. you can get general ideas on wheels from here on FABO but the issue is no two of these cars are built the same. So what one person may get away with you may not due to individual vehicle differences. Of course as always these are my thoughts. I say it's your ride do what you'd like. No disrespect meant. Have fun.