[Dovecot] Proxy to join two accounts

[Tomek]

Hello,

I have server with IMAP on dovecot for user mails and second server on 
archiveopteryx as mail archive.

I'm wondering if it's possible to make some sort of proxy to these two 
servers in way where:
- dovecot server will be main IMAP service with INBOX, etc
- I want archiveopteryx account to be something like shared folder with 
read only access (no delete, no move, etc) in path ex. /archive/user.name
- this proxy mappings should allow adding few archive accounts to one 
user (in case of people replacement)
  + it will be cool if this mappings could be defined in database so I 
could write tools to manage archive access for bosses.

Is such case possible to achieve with dovecot (any howto or example 
would be very helpful)? If not - do you know any proxy tools that could 
allow such configuration?

Thanks for any help.

Regards,
Tomek.