Even though this as a novel idea, I see it as a non-starter in the US simply because:
1) You're highly unlikely to get a license to operate it. Even though your premise of using it for EMCOMM, I think you will still need a license or suffer legal ramifications. And once the local cell service providers find you have it, they are going to pounce on you like a pack of dogs on a 3-legged cat!!! You'll be up to your keester in lawsuits for everything you can think of related to cell problems from then on regardless of whether you're even in the area or not.
2) How are you going to stop the 'common folks' from using it once they see they have 2,3,4,5 bars of signal? They will quickly overload the system in many areas. Without sophisticated encryption and firewalling, your probably going to be fighting a losing battle once deployed since all your APPROVED users will have to able to get past the blocks to use the system.
3) How are you going to power it if there is limited power from generators and batteries to be had in the area? I didn't delve deep into the specs but I'm sure it will take more than a few 'D' cells to keep up for any length of time.
4) Coverage is going to be severely limited to a very tiny area in many places. Heck I have a tall commercial cell tower just down the street from me an have a hard time getting decent signal time to time.
Just food for thought ......