Novel proof of pumping lemma for regular languages
Essentially the same argument is made by Andries P.J. van der Walt (1976, Lemma 2.3 and Example 2.9) for the variant of the pumping lemma where $N$ letters are marked and all three of $x$, $y$, $z$ must contain marked letters.  See also Autebert, Boasson, and Cousineau (1978) for more properties of abstract families of languages satisfying this variant of the pumping lemma.