emac gnus-centric gmail-phobic multi-host mail management

[regcl]

Sorry for the length of this. Please let me know if I am posting to the
wrong list.

I use a lot of different machines including mac os x desktops/notebooks
at work and home, Grid engine cluster submit hosts reached by ssh and
compute hosts reached by the grid engine qrsh commend at various work
sites, and debian servers at home.  I use emacs 24.3/tty everywhere,
which I build from source on most machines.

I have been using gnus for about a year as my mail client, and it works
everywhere. I am just starting to use newgroups.  

I want/need to modify my mail approach with these objectives:


A) Sweep mail off of the servers

Currently my mail is mostly served by gmail + an an exchange server,
either from work accounts administered by my employer/institution or
personal accounts and accessed by IMAP. I want to stop using these
servers as my master mail repository and reduce the amount of mail left
there to a minimum. So, I need to sweep mail off of accounts into my own
mail repos. The approach needs to support compartmentalization, by which
I mean that at home I need all the repos (personal and work) and at work
I need only work related mail repos.


B) Sync the gnus view

I want to sync my gnus view of mail and newsgroups so it is consistent
and up to date on all machines. Once again, this needs to be
compartmentalized. At work I want to see only the work-related stuff, at
home I want to see everything.


C) Compatible mail repo/backup scheme

I need to park the mail I am sweeping somewhere, once again with the
compartmentalization issues. While I use emacs as my primary email
client, it would probably be wise not to lock myself in to emacs, so
maybe I want the mail in a form compatible with other clients on my mac
os x desktops, most likely mac mail.app. What is the lightest weight
approach here? Is it maildir with dovecot/localhost?


D) Replication of the mail repos.

I don't think I want to put up a pop or imap server on the net, at least
not now. So I am thinking the problem here is primarily one of
replication of my  mail directories across machines. Am I right?

Based on my limited reading about mail, it seems like this could be done
with IMAP, but I know zilch about IMAP and I don't have a place to park
a personal IMAP server on the net.  

On the other hand I use git for all of the other replication/syncing
that I ever do. So here is the question: Can I park my mail in maildir
with sub-repos for work and play, and use git for replication between
machines? What would be the pros and cons of this approach vs learning
using IMAP?

Thanks in advance,
regcl