[Dovecot] Dovecot proxy in front of UWash?

Is it possible to use Dovecot frontends in front of UWash backends?

I need a proxy pool ASAP. There is not sufficient time to migrate the backends for 40,000+ users so they have to stay UW for now.

I have been looking at Perdition but concerned about performance under load. Dovecot looks really promising with it's non-forking mode. I need simple dumb frontends no local mail.

Other questions:

1. Database? Wiki only talks about SQL, can I have it map username to hostname using LDAP or some other mechanism?
2. Kerberos? I am hazy here, but can I have the frontends auth the user via Kerberbos and things "just work"? Or do I need to stick with PLAIN authentication?
3. Port mappings? Can I have the requests coming in on SSL ports remapped to non-SSL ports on the backends? Thus the backends could have their load reduced somewhat. e.g. client->proxy:993->backend:143