Hmm, that's interesting, actually.
Indefectibility of the Church is a powerful argument when I hear it. I think the first time it really was busted as an argument was when I learned that the translations into vulgar languages are in no way indefectible. Hence the "for all" "for many" debacle.
Recently I've been thinking that perhaps the nom is indefectible in the original latin (which nobody uses), but that can't be. The NO doesn't seem to be Catholic at all, imo. This argument about stability makes sense to me, really. I've asked myself numerous times before learning about tradition, "If the Church is indefectible, why do they continually make changes in the Mass?" I mean, prior to this century, how often was the TLM adjusted? Not very often at all, as far as I'm aware...and never the words of consecration. Heh, even as a new Catholic I was sensitive about anybody making changes to the Mass. Not sure I knew why, really.
I think that the changes which they are having to make to the NO serve as evidence that, whatever it is, it most certainly can't be authentically Catholic. It should be a fearful thing to make even the smallest adjustment to the liturgy...but they aren't concerned at all.
Anywho, I enjoyed reading your post, thanks.