Eric, let me jump in here.

I too spent copious amount of time on many many calls with Verizon and Winegard.
The net result was, yes, the Winegard product does support a Verizon SIM however it needs to be activated correctly with a data plan only with the correct product type in the VZ systems..

I had mine working albeit it was inconsistent with network service - it registered on the Verizon network but it was setup incorrectly on the VZ network system and kept disconnecting from the network when VZ back end systems do a sweep for unrecognized or suspicious devices on their network. In the end, after speaking to VZ product to get a Winegard setup on their billing system, and VZ 3rd line support couldn't reconfigure the original SIM so I needed to go to a VZ store and get a new VZ SIM, re-associate the new SIM with the Winegard and have it re provisioned from scratch.  

My setup is now 3 phones with unlimited data plus one data plan SIM ( winegard) with a 15gb or 22 gb cap ( they say its unlimited but you get knocked down to 600kb once you get to the cap. OK for email but not for streaming netflix. We ended up using our hotspot data on our phones with the Winegard  and swapping between our 3 phones to use up our unlimited plans by the end of the billing cycle then go back over to the data plan SIM. 

Hope that helps.

best,

William