Multiple logins with AFP+NFS home directories?

Hi everyone. I have a relatively simple setup with an Xserve+RAID hosting home directories and such for client machines. User home directories are mounted via AFP. The machine also exports the home directories via NFS for use with a few Solaris boxes. I have a small number of very fast machines, but mostly older G4 iMacs and eMacs. Most of the CPU-intensive stuff we do is command-line and/or X11 based, so I'd like to enable it so that users can login to the fast machines via ssh and run stuff. Here I run into the classic multi-user problem: I can't have two users whose home directories are mounted via AFP logged in to the same machine at the same time. Is there a solution to this problem? For example, is there a way to mount a home directory via NFS when you ssh in, but via AFP on the GUI? Should I just scrap AFP entirely? I've seen mention of this problem all over the place but have never seen a solution before. Any help would be greatly appreciated.