So I'm thinking a Raspberry Pi board would be perfect for what I want.

the Novatel USB760 drivers say noarch so they should work on the ARM board, right?

I think if I put it inline with a WRT54GL (free - I already have it) with Tomato or DD-WRT, I should pretty much be able to do whatever I want. All the Raspberry Pi would have to do is pass through the network connection to the LAN port.

I realize I could use the Pi as the router itself, but I'd like to keep the setup as simple as possible for the guy I'm training to run this here. Any thoughts or suggestions or see any problems with this idea?