GBAS could be more feasible. The cost to put in GBAS is about equal to an ILS for each runway end, so cost would be a wash.
I would like to see the GBAS approach procedures (and departures) re-thought in the criteria.
First off, there is no reason it should not be CAT III at this point in the game.
CAT I, and 250 HAT, following ILS criteria is not where GBAS should be at this point in time.
RNP transition from the STAR to GBAS 0.1 CAT III final is where this should be at. ASA as 50% owner of SmartPath should have the system at every airport in AUS, and should be dictating the criteria to ICAO.