I agree with all of this pretty much besides turtwig and snivy, they should both drop a tier.
I feel like there should be inbetween ranks of A+, B+, C+ etc. tho. For example, Azumarril can be caught early on, has a monstrous attack stat when taking Huge Power into account, great neutral coverage w/ its STABs and gets all the moves necessary (bar Aqua Jet) through level up. It is most certainly better than all A rank pokemon, it may even be on par w/ torchic tbh, but if not it at least deserves to fit into an A+ rank bc it is so much better than every other pokemon at that A level.