Good to hear from you aterpster!!!... All good and partially valid points, ...but there are still reasonable and useful low cost and high capability ways forward, with both RNP and GLS.
First, there are vastly better ways to do the GQS than FAA did, just as we did with many "near in" issues at [real] RNP sites. If an aircraft can safely operate visually at all, then there are ways to do both real RNP, as well as to even qualify the runway for using LAND 3/AIII or equivalent through rollout, as well as addressing safe OEI balked landing protection from the TDZ. There are VERY few true and real "one way" in and out runways globally, which may need to use an explicit commit point. As to cost, neither GLS nor RNP needs to be expensive. They are presently only priced the way they are for largely non-technical commercial reasons, that the marketplace could easily solve, and likely will eventually solve.
Yes, I've flown LPV, as well as FLS and IAN,... (extensively) as well as nearly every other All-WX-Ops idea (good or bad) from the days dating back to the '60s. Col. Carl Crane and I even discussed it back in '73, while flying with him at Wright Field, with a demo of his "All-Weather-Flight-Gage" dating back to the '30s! So while LPV might have been a reasonable idea back in the period of 1969 through '71, at the advent of autoflight systems like the SPZ-1, PB-100, or FCS-110, and the related nav systems like the TERN-100 and AINS-70, ...LPV is still obsolete trapezoidal, angular, straight-in, and horrendously airspace wasting criteria. As a concept, it no longer makes any sense at all, since we first first did linear RNP .15 around the corners at KEGE back in 1991, and later at the first real "published" formal RNP at PAJN in 1994. RNP is ALWAYS better, safer, more usable, and a better long term solution than any LPV (especially when combined with GLS/GBAS). RNP could have been (and still could) be done for FAR LESS COST and far more benefit than WAAS/LPV, for everyone from tiny UAVs, to GA, to the largest wide body's and DoD vehicles. Unfortunately, it was largely AVN, AIR-130, and later AFS-400 that set GA on this foolish course, with having had no vision, or credible experience, or technical capability, or understanding of the true system and operations level risks involved whatsoever (versus their naive and seriously limited and flawed CRM assessments) ...that screwed this subject all up for over two decades for nearly all the world. So now WAAS(SBAS)/LPV is an entirely obsolete waste of money for everyone, with a lost generation of avionics that will never solve NextGen economically, safely, or efficiently, that needs to simply be phased out at the earliest opportunity, before it further fouls up major portions of global airspace and ANSPs. When we're already landing "critical risk to ship" UAVs on pitching rolling moving decks within 1 ft laterally, and 8 ft longitudinally with these concepts or equivalent, while safely and routinely missing nearby obstructions by a few feet, as well as safely and softly landing other UAVs for pennies per landing (with systems like Portabas), ...then still continuing to unnecessarily lose A320s at CYHZ, or A330s at VNKT, or B777s at KSFO is absurd.