This can be a sticky one. Thank you for starting this thread.
Can the Squarebox guys pitch in on this?
We generally don't move files once they are in place, but you should be able to do this.
Using a full path to proxy, which makes managing large proxy sets easy, this is the system path mapping.
I've heard of making all proxy in a single folder but this doesn't work as expected. We are normally moving via automation so we can just relocate the proxy to match the new path, but a stand alone user can't really do this.
Is there a fix for this other than moving the proxy? Great tutorial subject here.