They can do it right now without altering the game at all, without any kind of NFTs, and second, the have the cake and eat it and sell it stuff doesn't work, the money that this guy is getting paid has to come from somebody, and the moment the balance is broken a more ask for a payment, well....you end like Axies!
A game's economy to work has to offer a complete manufactural proccess, since raw materials to final products, which have real usage and impact along the development of a player inside the game.
In games like World of Warcraft and Runescape Real World Trading has been practiced for more than 20 years already, because there are people who enjoy the game, but don't have spare time to grind money and items virtually. It's similar to what NFTs attempted to introduce in crypto industry, with the difference that there it works. Now imagine if bots were cut off and only legit players had the opportunity to earn from it. I think the environment would be pretty stable. For me it looks workable.