@Underfire, regardless of number of channels and number of approaches &/or departures supported, each GBAS system is still limited by the physical area of coverage and maximum use areas for the installed system. So if you have aerodromes sufficiently close and dependent on runway alignment, one GBAS system could in fact support multiple aerodromes.
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.
Acknowledge your comment re difficulties in transitioning GNSS to ILS - mainly because the boxes weren't originally set up to handle the transitioning from one nav system to another in that fashion (different integrities, different ways of handling the nav tolerances and so forth, transitioning of CDI, etc.
Re aircraft options, obviously bigjet world is centred on Airbus and Boeing, but there are a lot of RPT aircraft that come from other manufacturers (not to mention legacy systems
) - hence the comment about current limited applicability of GBAS as far as users (operators) go.