mirroring debian-security, sharing package pool with stable/testing/sid pool

[Zenaan Harkness <zen@freedbms.net>]

I currently know to some degree, and use, debmirror.

I admin/help-desk for quite a few people in a rural area - the PCs I
admin are typically only connected to the Internet via high-latency,
low-bandwidth internet connections.

So, I run a debian mirror from a particular host which has a
high-bandwidth internet connection.

I then sync against this mirror every {random period of time,
sometimes a day, sometimes a week or more} and then use that sync'ed
mirror to update the various other PCs I admin.

Does it make sense, that when I connect my sync'ed USB drive to a
computer I am updating, that an apt-get update would also update from
a local debian-security mirror?

I could create a mirror from, eg, mirror.aarnet.edu.au (I'm in
Australia, and our ISP peers its free zone with aarnet).

I just began this process now, but stopped it when I realized that
there may be overlap between the debian-security package pool, and the
normal debian stable/testing pools.

Thus my question:
Is it possible to use debmirror, to mirror stable,testing,sid as well
as debian-security for stable and testing, and have them all share the
same package pool?

I can't see it, and I'm hoping I am simply not understanding
something. If I would have to go to a more advanced setup with some
other debian tool, I am willing, but that would take some time (namely
finding the time, so would not be immediately).

TIA
Zenaan