Why does the Foxtrot have to be at 5 miles or there-a-bouts, why not somewhere like where the profile intercepts the minimum straight in commencement altitude?
This has probably been inherited from the fact that most approaches (VOR, NDB, etc) have their FAF around 5nm to run to the threshold (though there are a few places that this is not the case, the Tumut, NSW (YTMU) RNAV comes to mind). Though I suppose you are really asking why does there have to be a waypoint for the FAF not just a fix based on a track and distance to run to the MAPT and have the GNSS unit conduct it's required functions at a much earlier point if it needs to rely on a waypoint for it to happen. I think the previously mentioned approach at Tumut is coming close but not fully to what you desire.
I do apologise for the thread drift.
On topic however I do agree that SBAS is long overdue to be brought to our part of the world. There are many regional as well as major aerodromes that can benefit from the advantages that this technology can bring (an LPV approach for runway 33 at Cairns comes to mind as there is only a localiser approach for it and guess which runway is typically in use during the wet!).
Anyway thats my 2 cents along with plenty of inflation.