Have you considered just having a hotspot that you take along with you in your vehicle, or even in your pocket, than to tie up a moblie radio, a hotspot, coax and antenna, just to get a few miles range out of that setup. For less than $100, you can get a MMDVM hotspot device, and use your cell phone as the bridge to the internet. People do this all the time, so your idea would actually limit your range of operations, and cost a bit more.
For years, I utilized the DVMega digital modem board and the add-on BlueStack board, which made it unbelievably simple to do, as it used bluetooth to connect the modem to your phone, with a convenient app. I never understood why people went with the more complex openSPOT or Pi-Star devices, as they had to deal with network setups and such (even using small portable routers in their cars, before the openSPOT had internal WIFI). I guess hams like to do things the complicated way.
