Use of variables within archive rulesets

[Alex Neuman van der Hans]

I've got a few clients who choose to archive all their incoming and 
outgoing e-mail using the "Archive Mail =" function, using a ruleset 
such as:

From:   alice at domain.tld   /home/archiveaccount/mail/outgoing/alice
To:      alice at domain.tld   /home/archiveaccount/mail/incoming/alice
FromOrTo:   default   /home/archiveaccount/mail/BCCs

... so that mail from alice and to alice goes to the "alice" 
IMAP-accessible "folder" on the "archiveaccount" user's account, and 
those that aren't covered by any of the rules (such as BCCs, users I've 
forgotten to add to the ruleset list, and funky NDRs and stuff) get 
archived to a separate "BCCs and such" account.

I'd like to know if it would be possible to use some sort of variable 
(systemwide or generated) that would allow me to do something like:

From:   alice at domain.tld 
/home/archiveaccount/mail/%year%/%month%/outgoing/alice
To:   alice at domain.tld 
/home/archiveaccount/mail/%year%/%month%/incoming/alice

How would one go about this? I believe I'd have to create the structure 
first and change the ownerships and permissions so that the user 
MailScanner runs under can write to it, and the "archiveaccount" user 
can read from it, but besides that I wouldn't know where to begin.

Suggestions?