Instead of transferring the internals to another case, you do the complete opposite. With the proper size torx-bits you can remove the front face plate from each machine and swap them out, as well as the back of the machine, of course. You could re-attach the internal fan via double-sided tape. That should help you increase the value of the Mac.
The only possible issue that I am not fully aware of is serial matching. I don't recall if the serial number is etched or stamped on the internals anywhere, as well as the case. If not, than you should be good to go, and no one would be the wiser.
Hope this helps...
Hey, thanks! Now I have to go buy some torx bits and learn a little bit about the insides of these compact Macs...
scary.