All of the chat so far has missed one essential point. There is already a CTAF for military low level traffic. It's a common frequency for all low flying areas. But it's on UHF. It's in common use - more by some units than others - and is typically used by FJs as they descend to enter low level (thus having a bit more broadcast range than if they did it only when at low level).
But since civil aircraft don't have UHF, and as far as I know there is no mechanism for military aircraft to simultaneously transmit on UHF and VHF, the only way this facility could be of benefit to civil traffic is if they moved the CTAF frequency from UHF to VHF.