I feel your pain here - We have many Z1 and Z3 units out in production and numerous very remote sites, running Cell only, mostly Verizon. The old Pantech 295s work great for us, but are discontinued, and long in the tooth obviously. We have also had success with a couple of the 620Ls we have out there. We have NOT had any success with the 720L...tried them, and have a couple out there...but they are very unreliable and go down for hours at a time...then magically start working again for a week. We've gotten to buying 295s off Amazon to get some of these emergency sites up!
The Z3Cs didn't support Verizon carrier when I tested them (which seems crazy....), but I had it working on Verizon fine. But they are much more expensive, not to mention the maintenance a lot more expensive. And until they are officially supported on Verizon, that kills it for us anyway. But some sites will balk at the price tag anyway. However, more and more it is looking like the likely solution for us once Verizon is officially supported. We have some newer Feeney modems in for testing, but I am very wary of USB modem solutions and meraki right now.
That is interesting the 730L has been removed from compatible list...I didn't know that until reading it hear. It was still on the good list when i opened a ticket with them and stumped several of the techs, most didn't want to mess with the issue at all. Agreed...if you are truly not going to support it, then don't put the port there and market its ability for this.