Everything driver-related is a kernel thing and since Easy Debian runs on top of the Maemo kernel it can't make devices work that don't run in Maemo.
Your best bet would be to ask the kernel power team for support. But first try to find out if it's already supported. Try to find a how-to that describes how to make this modem/card combination run in regular x86 Linux systems without the use of GUI tools!
If you don't know how to do that please connect the modem with the card to an x86 Linux system and provide the relevant part of the output of:btw: Have you tried to run the Aero 2 card in the N900's internal slot?