Accessing the tower is expensive in time, and equipment that runs at the tower is exposed to a wider variety of temperatures and RF stress than in a nice warehouse somewhere in the metro area.
It's possible the right caching at towers could reduce the backhaul bandwidth requirements, but seems iffy.
How much latency do you think is incurred between the ISP and cell tower?
Not saying no here, just pointing out a very large concern.
My concern is cert/key management where the edge is somewhere you have very little control over, like a cell tower, random building network, or a users house. Even with keyless, once that device is in my home, Im pretty sure that entire thing can be reverse engineered. Not easy, like probes and oscilloscopes on exposed leads hard, but physical access is pretty much game over, no?
I've worked in this space and the solution is detection and mitigation. Limit the damage to single devices, workflow the user in, look for human attack patterns. Defense is futile.