Actually, I agree with you, I don't believe we can sustainably fulfill a demand for meat, especially beef, at the current rate that this demand is rising worldwide. But I also think that this demand is not a true need, rather it's an artificial need that is created by the over-supply of cheap meat by the food industry. Kind of like nobody needed to have smartphones, until everyone had smartphones and now everyone wants to have a smartphone because everyone else has one.

So I think it's a matter of controlling over-supply and reducing the excess of demand. One way I think could work to do this in a way that aligns with middle-class values is to promote a return to traditional, local cuisines and diets. For example, I come from a Mediterrannean country where the majority of the traditional diet is, well, typically mediterrannean, 80% vegetables, pulses and legumes, with tons of olive oil and tomato sauce on everything, and with meat eaten sparingly and most of the time replaced with dairy. Almost all traditional dishes are either vegan, or vegetarian because they include eggs or dairy. We do eat a lot of fish, which is also rapidly becoming impossible to produce sustainably, so that's another discussion to have. Of the meat we eat, most of it is chicken or pork, with sheep or goat eaten a few times a year, as a traditional treat during religious feasts.

In the place I live, sheep and goat farming is free range almost exclusively. I'm afraid pork production is another scandal of animal abuse, not different than factory farms for cows. The same goes for chicken, treating animals like industrial goods must absolutely be made illegal and damn the markets. On the plus side, pork and chicken are much more sustainable from an environmental point of view- and both kinds of animals are absolutely fantastic recyclers of matter that humans can't even consume. Incidentally, the traditional thing to do with whey left over from cheesemaking is to feed it to pigs. When my cheese fails, I feed it to the chickens :)

To my mind a large part of the problem is that most people choose to live in cities, away from food production. This has two effects. On the one hand, the people in the cities have no idea where their food comes from, they're insulated from the reality of animal abuse in factory farms and they even lose the ability to recognise good produce (both meat and plants) from bad. On the other hand, because the location of people is massively centralised, the production and distribution of food also becomes massively centralised.

In simpler words, it's impossible for everyone who lives in the city to have their little garden with their veg and a few chickens or a goat. Instead, the farms are all outside the city and the food is all in the supermarket shelves. If everyone could raise their own animals, grow their own vegetables, we would obviously be in a very different world, with far less animal abuse (certainly far less systematic animal abuse) and far less over-consumption: it takes a lot of work to care for an animal, it makes more economic sense to keep an animal for its milk so one can have dairy year round, rather than slaughter it and eat meat once, and it's also much harder to mistreat or even slaughter an animal for food when one has raised the animal from a baby (one will always find excuses to not do it today).

So a simple solution would be to keep the food where it is produced: in the countryside, away from the city. But then the city folks would literally starve and it wouldn't be about meat or veg anymore, it's just impossible to grow food in the city. So it's not really a practical solution at all.