Other filtering factors: size and formfactor, slot keying, usb requirement and that voice is possible.
If and when there are going to be more modems available (and actually already now), L5 will need a software that identifies modem and installs the right drivers, changes required settings and permissions, checks modemmanager compatibility, sets up sound/voice, informs user of the modems features and limitations (what bands / intended geo-area, available G’s, dl/ul limits), and verifies that sleep feature works (or disengages it). And if modem is not recognized, not in L5 db, helps with manual setup. Some kind of L5 specific known working/usable devices library, I quess. I think we’ve only touched the surface of what cards may become available and somehow those should be managed by users in a friendly way.