What I really want is for the existential quantifier to become distinct from the "at least n" operator. In my preferred version of cekitauj (the cmavo swap dialects) the existential quantifier is spelled {su} and the "at least" operator is spelled {su'o}. This split is not possible in official Lojban, unfortunately, but it would keep the symmetry intact.
Would "no" become "no'oi" as well?
Yes, I believe it must and should.
{so'e jbopre cu banka'e lo .inglico} ("Most Lojbanists speak English") cannot be expanded like a normal numerically quantified statement:
? su'oi da poi jbopre gi'e so'e mei cu banka'e lo .inglico
"Some xx that are Lojbanists and most in number speak English." [1]
Quantifiers like {so'e}, {so'a}, ..., so-called proportional quantifiers, require there to be something they are proportional to. The number of broda in e.g. {so'e broda cu brode} is compared to the number of (all) broda that brode. "Out of all the Lojbanists, most of them speak English."
So I would say that
ru'o da poi jbopre zo'u so'e de poi menre da cu banka'e lo .inglico
"All [the] Lojbanists taken together are such that most of them speak English."
is a better (intermediate) expansion. (Getting rid of {so'e} entirely is possible, but I'm too lazy to type it out. The proportion is >0.5)
But {me'i} and {za'u} can be considered prefixes. I had thought {me'i PA da} would mean {su'oi da poi me'i PA mei}. A definition in terms of {ru'o} would also be possible, but I'm not sure that it would be better. It would mean allowing prefixes (like "<" and ">") to turn non-{ru'o} numerical quantifiers into {ru'o}-type quantifiers, and this requires a good justification.