Roulette,
You said:
The multipath I was talking about may or may not influence how the GBAS system is set up (on the ground) and ultimately the maximum areas of use. Ditto for terrain. This has nothing to do with the VHF transmission of the procedures to the aircraft.
What "multipath" problems are you referring to?
As for your
"limited applicability of GBAS as far as users (operators) go"
how is that different from RNP for legacy aircraft? Surely we have to start somewhere and these systems will exist in parallel for a long time until one or the other gains the ascendancy in operator choice?