That is a nice post.
It looks like most of the mvc frameworks already follow YAGNI, implement logic in models, send response through helpers and put all series of actions in controller.
What you describe is more design and architecture. YAGNI may have lead to these decisions. But where things go is not focus of YAGNI. YAGNI is about implementing things when you actually need them, never when you just foresee that you need them.
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