Sorry, but in my eyes the proposed structure has already got a hole in it, in that IMO what you're calling "GM's say" and "System's say" very much overlap. Why? Because a GM can, if desired, redesign or kitbash the system into what s/he wants to run.
What you're seeing above here is not "my proposed structure having a hole in it." What you're registering is your deeply-internalized belief of the assertion you make directly below being challenged by a proposition (more on that below):
First thing: you seem to be assuming a level of design tightness and resistance to modification that - while good for cars and many other things - is almost antithetical to the make-it-your-own-game philosophy that's been deeply ingrained since day one; a philosophy that really does set RPGs apart from almost any other type of game and, one could argue, almost any other type of product design. Take away that philosophy and you take away much of what makes the hobby what it is.
On the first bold word, I'm not "assuming." I'm "proposing." My proposition is "what if there is design tightness and resistance to (
foundational - you omitted this) modification in a TTRPG system (just as there is in biological systems, plenty of engineered systems and in plenty of art).” You've inverted what is happening here.
You are
assuming that there is no such thing as a level of design tightness and resistance to modification. You then index this assumption (that, given our interactions over the years, is clearly the cornerstone of your ideas around TTRPGs) when you relate your ideas on "the essential philosophy/culture of TTRPGs (or something like it)" directly thereafter (the second bolded part after "assuming").
Your position (which I already knew) is "there is no such thing as
system's say (or
designer's say) because GM."
I already knew that about you. I'm curious why that is.
If I had the a) skill and b) equipment to record what's in my head I'd be doing this all the time!
So
this is actually useful to our conversation.
This is what I was trying to tease out.
So, beyond the TTRPG essentialism/"beating heart of TTRPGing" you're espousing above (and have espoused many times before), you're actually talking about how the sausage is made here. So, presumably, the driver's experience, music consumption, and art consumption might/would all change, at the macro-cultural level (just as you've specified your idea of a macro-cultural essentialism of TTRPGs), if humans
felt (I use the term "felt" here very deliberately) that they had the "the chops" & means (skills, tools, kit). All cars, music, and art would change status from "completed works" to something like "pending DIY projects?" Do you think that might occur? If you don't think that might occur, maybe break out why TTRPGs are particularly unique here in the way that cars & driving experience and music and art consumption are not (indexing the owner/primary participant relationship with them if you would...because that most closely maps to something like your personal usage of "GM").
Can you engage with those questions/propositions above?
* In case its not clear why I used "felt" above, I would hope its abundantly clear that the human expert class is overrun with a hubris that renders their perception of their own expertise significantly more a burden than a boon (even in the discipline that they're supposed to be an expert in). Ironically (given that you believe GMs DIYing is the backbone, or near enough, of TTRPGing), I would say GMs in the TTRPG community are like the
paragon of this phenomenon.