Yea, that sounds like a good idea, can you do that in something like a pre-push hook? That plus long reflogs seems like it would make recovery of rebased/deleted branches really easy for end users.

We don't allow force-pushes without admin involvement, so rebasing isn't so scary for us, but we do cover it that way. And we got the undo operation down to a command on the infra: http://community.kde.org/Sysadmin/GitKdeOrgManual#ohnoes

The rest of that Wiki page is also pretty interesting for a general look at what devs can do on git.kde.org - server-side personal clones, personal repositories, a personal trashcan for repositories, etc. We don't have a pretty web interface for it (yet?), but it has some nice features.