Just a couple more random points...
I wasn’t faulting the founders and early workers, only pointing to the futility of continuing at the present. Things beyond FOPL were just not thought about even in graduate classes in the 50s and 60s, though they did take off rather rapidly then (I went to my first Monatague Conference in 1973 or so, with all the hot shots present and talking above everyone’s heads).
If you were there in 1973, I envy you. You witnessed history.
Some minor points: Montague’s quantification paper came out in 1960 or 61.
Sorry, sir, but I believe you're off by 10 years. His first two big papers introducing his system of analyzing a "fragment" of English as if it were a formal language came out in 1970, and his most famous paper Proper Treatment of Quantification in English was published in 1973 posthumously. Montague had earlier papers, but they were on (I believe) set theory and not related to his "grammar" (really semantics). And as you yourself point out, even in 1973 it was a small closed club of people who actually understood what he was talking about. The earliest Montague paper dealing with language was 67/68 I believe, but it's been overshadowed by the more famous three that came out later.
He did know mereology, courtesy of Twardowsky, but didn’t see its relevance.
I am sure Montague was aware of mereology, but it does not figure into his system. I can look up the dates, but I also believe plural logic was not even on the scene prior to 1973 (Boolos(??)). Interestingly, Barbara Partee has been deciphering Montague's private notes (written in a private shorthand) and she reports that Montague was privately flummoxed by the logic of some sentence in English involving plurals. As a person who has read the Jboske archives, that made me smile. If he had lived and wrote the book that he was planning on writing (which would have been a classic and which we've been robbed of by fate, in my estimation) I believe Montague would have been forced to deal with plurals (and masses), just as jboskepre were so forced.
He was a Tarski student, which put some limits on him (an antipathy for Quine, for exampe -- another possible source of mereology)
Quine was a foundations-of-math guy, and his famous disdain for intensional/modal logic is fine for a certain approach towards math, but it's completely inapt when applied to human language. We talking humans use intensions constantly; they need to be handled like they're real values for expressions. In other words, nonexistent things are part of the model; nonexistent things absolutely do figure into the value of words -- even if one has qualms about their existence. (Actually, one should have ontological qualms -- that's the whole point -- but semantic qualms are impractical.) Quine himself remarked upon his review of Loglan that he thought that human language was too messy to be logical and therefore, though Loglan was interesting to him, he thought it was hopeless. Mind you for Quine "logic" by definition excluded modal logic. I can dig up Quine's exact quote on Loglan if you're interested (not the one JCB circulated).
In short I don't know why Quine has had the influence he has had on Loglan/Lojban. His idea of logic was far too austere to be used as a basis for human logical language. Kripke's work is much closer to the mark, and it was Montague who noticed this and showed how modal logic could be used to (directly) analyze English.
As I think (hope) I said, it may turn out that some Loglan will be right, it is just that it will. be impossible to prove it so by the present system. JCB, by the way, knew more logic than Lojbab (and got better grades, too), so we don’t want to be casting that as an excuse for a bad job at what he was doing. He just was a terrible experimental designer, though he did well in social psychology.
Yeah, it took me a long time to figure out how Montague (et al) ought to fit into this scheme. I got caught up in the project and am bad at adding one and one. (I actually don’t think that Montague’s system itself is too relevant; it is the overall pattern that counts and that is largel Chomsky, which was available to JCB from early on.)
If someone was enterprising enough, they could write _Proper Treatment of Quantification in Lojban_. Any takers?