@rjtjrt: It isn't pie-in-the-sky at all. We have all the accuracy and integrity we need for most GA applications ... right now. Further with a decent filter design, low cost inertial (e.g., a simple PIPA or PIGA or gyro is inertial), and GPS+Galileo, Baro VNAV, and perhaps even benefitting from an RA floor, we could even be using RNP toward Cat III minima in GA. I can cite safe and successful RNP .1 approaches and departures for GA that could be flown even by a C172, that with appropriate criteria modernization at authorities, such as the application of [properly implemented] FOSA, could easily be IFR/IMC qualified for minima at least as good as any LPV minima, and without the airspace wasting straight-in angular restrictions of LPV. Hence, WAAS/EGNOS/SBAS is an idea whose time has come, and gone, just like MLS. It will just take some additional time for GA operators and small airplane manufacturers to realize it. Movement toward recognition of fully allocated costs, and asking those who still want WAAS to pay for it, will only accelerate the inevitable SBAS phase out.