Why is it that for many thousands of years the native bees survived and through many different situations?
Take your buckfast bee you buy one in leave it a year or two and have to buy in more because the stock shows f2 or f3 aggression (that is a human manipulation that will have lasted less than 3 years without requiring yet more intervention, many thousands of years is significantly longer than 3 years is it not?)
How many of these other domestic stock you talk of open mate?
No like most things when humans think they know better end up making a mess of things, bees are a good example, kray fish would be another, grey squirrels another. Keeping native bees suited to our climate that survive well would be the best reason for keeping them over imported bees, how do you think varroa mites ended up in the uk to start with?