Crab
Protection would be nice but if UK air ambulances were to try and set up TDAs for every broken leg they went to, the country would be awash with red circles!
Generally the fast reaction time to attending these jobs means that it would be totally impractical to try and set up TDAs. They are reserved only for Major Incidents in the Police/HEMS world.
I agree that a civvy version of TR+G would be a great idea. Both of our VHFs are taken up with monitoring local frequencies. But it's class G and keep eyeballs out.