While I commend your knowledge and experience with herps, I will have to disagree with you when speaking of Ball Pythons. The reason behind the majority being against feeding in a separate tank is because ball pythons can be picky feeders. Why put the snake through the added stress and possible refusing? Cage aggression is a myth as far as linking home cage to food. As you said, snakes are very much able to differentiate between a human hand and a rat. Assuming you are not playing / handling rats and then reach into your pythons cage.
Just because you have conditioned your BP to feed in the tub, do you think he would not feed in his enclosure? Because that is the same line of thinking as "if I feed him out of his tub, he won't prey bite me in his tub!" Bottom line, if you smell like prey, you have a high risk of being tagged. If its working for you that is awesome, and there is nothing wrong with that. That does not mean it is the best way for ball pythons or general hobby keepers.
Many will even go so far as to say you have a higher chance of getting tagged when using a separate feeding enclosure because you are handling / attempting to handle them while in food mode.
The way zoos and pet stores do things is irrelevant to how hobby keepers practice in my opinion. They are looking out for the possible mistakes of others (smelling like prey).
As I said, because it works for you that is great, but you also should understand that ball python husbandry has come a long way in the past 10 years, and just because it is currently working for you doesn't mean it is the preferred or recommended way.
Welcome to the site, and back to the herping world! We need pics of your cinni
Edit: Congrats on the conversion!