Archive to mbox? and other questions

I have a few smartlist questions:

1.  How can I save messages to an mbox file, where I can search it 
quicker and easier than opening thousands of individual message files? 
Ideally, I'd like to group the messages into mbox files by month.

2. I have an existing database of users, and I will be creating a web 
page where they can log in, see which lists they are subscribed to, and 
change their subscriptions.  What is the best way to synchronize a 
database of user enrollments with the dist list?  Should I rewrite the 
dist file from the database each time?  The alternative method of 
sending an email with an XCommand seems like so much overhead, 
particularly since I don't want any email response to the command, and 
because I may need to subscribe a large number of users at once.  Why 
isn't there a simple script, ala Mailman, for handling admin functions?

3. How can users select their own digest mode, rather than setting it 
globally for the list?

Thanks in advance.

-- 
Gary