“The point of focusing on Talmudic literature is that none of the rishonim had Techeiles, so anything they say is merely an educated guess albeit filtered through their knowledge of the aforementioned Talmudic literature.”
If the rishonim had no external yediah what techeiles is, obviously what they said was based solely on chazal. al kol panim you can’t argue on them from a yerushalmi. they knew yerushalmi- and as tos. in succah says the bavli isn’t mashma like the yerushalmi and tos. in chulin is clear it isn’t green so tos. also disregarded the yerushalmi. so maybe you have a kashya on the rishonim but you want to argue with them??? and what is wrong with changing the girsa? the gra did that so he obviously held it was a mistake.
i agree that maybe you have a point, however if you are not coming from anything more than chazal, you can’t argue on rishonim.