Most efficient for customer service: Shared mailbox or mail enabled folder? Or something else?

Currently at my organization (running Exchange 2003 and Outlook 2003), our customer service staff use a number of mailboxes (for different brands) to support customers.  These "support boxes" are simply users within Active Directory, who I have then given read and send permissions to the customer service staff.  As our organization continues to grow, and we add more and more customer service staff, I'm finding it increasingly difficult to manage these permissions and changes on a per brand level.

The biggest requirements I receive are that the staff must be able to send as the support mailbox, but of course with the way it is set up now, all email sent out read "Sent by: John Doe on behalf of Brand Support."  This is annoying, confusing for the customer, and doesn't really shield our representatives from having a clever customer figure out their personal email address, causing loss productivity.  Originally I could have dealt with only one support box, but the inability to have the From: field send as an email alias instead of the primary address (aka support@brand1 vs the default support@brand2 set in AD), forced me to create multiple boxes.  It's messy, I know.

Another problem I am constantly facing has to do with auto response messages when sending to these support boxes.  Originally they were configured as rules, but we ran into problems when some customer also had auto responders on, creating infinite loops.  Then, these rules were switched to use the Out of Office Assistant within Outlook, in order to take advantage of the one response a day limit.  The problem with this is that customers receive an email with subject "Out Of Office Reply: <our custom subject here>," and I can't figure out how to disable that prepending text.  Of course the biggest pain is when managers want that message changed, I have to physically find some unused box, log in as the support user for that brand, and edit the rules within Outlook.  I tell you, I'm at my wits end.

I've read some about using mail enabled public folders, but am concerned about migrating all these thousands of email over to them, as well as minimizing downtime.  Would a public folder work for my situation? Will users be able to still populate the From: field, without the "sent on behalf" of message?  I know you can set rules on public folders, but can you limit it to just once an email/day/etc, without the Out Of Office notice?

Or perhaps there is some other way this can be done?  Any help would be appreciated, thanks.