I feel like this argument is very incomplete. Mudiay was in China. He was hurt there, and even when he played the Chinese team was unhappy. So I'm not sure with their import restrictions that we'll see that experiment again so soon.
There's the D-League where he'd actually work out for a coaching staff that's in touch with a real NBA team. What speaks against that other than the couple thousand you make less in the first year, or unless you have a really toxic personality that you don't want your client to display when you're the agent.
Jennings situation in Italy wasn't really thought through, because he went to a top team that had completely unrealistic expectations from an 18 year old who didn't bring size, strength or on court maturity to compensate for the lack of age/experience. There are better leagues and places that specialize on player development in Europe, and I'm sure they'd do it when a max 500k buyout is attached.
Australia takes away the language barrier and a part of the cultural differences on paper. So in these terms it makes sense. But the level of competition. Idk... GMs will see the high school prospect and I don't know if you want that spot in a draft that's projected to be as deep as 2017 is at the top.