Have you tried probing for 4G provider(s?) IP renew limits and IP allocation space size?
Things I can think of that would be interesting to know:
1. How uniformly distributed are the IP addresses you're getting.
2. The size of the IP addresses allocation space, assuming a fixed geographic location (I imagine this can vary a lot between providers and regions)
3. How often can an IP be requested?
4. Is there some sort of rate limiting? If so, how does it manifest itself (Sticky IP? slow reconnect? Something else?)?