readonly archive folders using squashfs

[Natu]

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