readonly archive folders using squashfs

I have a dovecot server running under CentOS using maildir format.  Due to the issue with minimum blocksize for files I would like to offer some kind of readonly archive using something like the compressed squashfs  where I would move messages to be archived to a maildir folder and then convert "cur" directory into a squashfs and mount it in place of the original directory so my biggest users could have readonly access to older messages without it using so much disk space.

Has anyone tried anything like this before and is dovecot likely to complain about the readonly cur directory?  If the complaints are minimal and didn't cause other problems it might be ok.  Any better ideas to implement something like this?

Thank You,

Natu