Either commit to 100 percent coverage or accept that areas you're not providing service for should be able to use frequencies there that you use in other places but not there.
There's no reason to give someone that kind of blanket lease.
Allowing others to use the same frequencies in a compatible manner would achieve the same benefits (improved coverage, since anyone can operate a tower) without the fragmentation. Not to mention that the cost of negotiating spectrum rights in each state/area would be significant, to say nothing of the fun issues that crop up along boundaries.
What is more, the fragmentation is a technological problem that is quiet easily addressed.
First, we can have catalog frequency. That is one frequency EVERYWHERE that specifies what frequencies other services are using in the area. As your device moves it will periodically listen to that frequency and update its database for that area as to what is used by what. This ensures that every device will at least be aware of what frequencies are in use and by what.
You have now added a second antenna to the device, increasing power consumption and complexity, not to mention the additional logic needed to decode the messages.
Second, the next technological problem is making your device adaptable enough that it can shift to different frequencies and possibly even different protocols. Most devices already do this especially smartphones. My smartphone has a bluetooth radio, a wifi radio, an FM receiver, a GPS receiver, a 2G radio, a 3G radio, and a 4G radio. I think it can also handle either CDMA or GSM. So that is already a very wide range of frequencies and many different protocols.
While I could be wrong, I'm pretty sure the norm is to have different antennas for most of those. Bluetooth and wifi can share one as they use the same frequency, but 2.4 GHz is so far from 900/1800/2100 MHz that it would definitely need a separate antenna. Even making an antenna with the desired characteristics at 3 discrete frequencies likely increases the cost significantly - covering a continuous range of frequencies like that without degrading reception would be even harder.
Your idea is interesting, but ultimately overcomplicated. The entire thing is basically a hack to deal with the fragmentation introduced, but it appears to me your real problem is that the current system grants a monopoly over the frequency. This would be addressed in my proposal by mandating that anyone can use the frequency, provided they were compliant with the protocol and associated regulations. (Or to put it differently, the spectrum would be allocated to protocols, rather than corporations.) It's not clear at all what advantages your approach brings over this.