Is it possible to use the Blackberry as an offline email reader? The mode would be: use the Desktop Manager to download filtered email to the device via the USB cable, read and respond to email offline, and then have the device send the email via Outlook when it is next connected to the desktop via the USB cable. In essence this would emulate a typical PDA workflow.

Is the reconcile email function equivalent to what I described above, or does it only move and delete as opposed to transfer, move and delete?

Has someone written a plug in for the Desktop Manager to accomplish this task?

No it won't work in the way you hoped. And I don't know of any 3rd party app that would enable it too..
I guess I don't know anyone who has ever shown interest in owning a BB yet not having the data plan.

I am one of the rare BB users that do not have a data plan… I won my 7280 at a Technology Show and I use the BB as a phone, contact manager and calendar. I would also like to do the same thing MrOcelot is describing above, unfortunately, the data plan is too pricey for me right now.

Unfortunatly it doesn't support the same type function as Palm OS in that regard. The blackberry is geared more for online use as opposed to offline use, where-as the Palm OS is the other way around. It's not possible at the moment, and I haven't seen any third party apps that will take care of it yet.