[Dovecot] Per-user IMAP enable - is it possible?

Just wonder if it is possible to enable/disable IMAP4 on Dovecot (2.0.x as far) on per-user basis?

The deal is simple: our policy is not to store a lot of mailing on mailserver (the user should store it locally), thus the 'use POP3' approach, but for a vary few users it is permitted to use IMAP4. But users sometimes simple miss the point that some mail clients (e.g. TB) 'prefer' to use IMAP4 first, and afterward I see mailbox full of mailings and no local store of it on user's workstation.

Sound too complicated, but setting up two Dovecots is not something I'd love to do as well.

Thank you for any ideas, Alexander