I'm sure if push came to shove the slow movement of hard-to-grow foods could be accommodated, it's not as though nothing else will be moving.
You've given this a lot of thought (and action, I think). Your posts on the subject are impressive, others here too like Mack.
Yet we don't come from quite the same direction.
"There is simply no room in a society built on the bottom line for mega beasts that don't serve a purpose (look at shire horses as an example)."
You used the word ethical - but in human terms would this not be called extreme fascist? You rate animals by default as useless, their usefulness to be demonstrated for even survival.
If you want us to keep any beautiful animals, what's stopping us? Just don't eat them. Don't lose those nice pigs! You've already indicated their usefulness - just don't try to industrialize it by making them a disposable commodity.
That said we have a difference of values, with regard to which your your posts make sense. Cheers