There was a documentary on the BBC a while back that would sometimes be on Google Video or YouTube that looked into the sex tourist resorts you're talking about but in the DR and Colombia. Seemed like a total scam to me for everyone but the guy running the "resort". The monger way overpaid for what he was getting with about 10 minutes research on monger boards and a fraction of the price he could hire a harem of girls for the week. For the girls, it wasn't like they were salaried, if the visiting American, Canadian or Brit didn't choose her, she didn't get paid. Just like the girls in the clubs and on the street. Effectively, the hotel owner acts as the middleman and pays the girl similarly as if she was working on the streets. The only difference is the sex tourist doesn't pay her directly.
Having been to Thailand, I can say I never heard of such an all you can have resorts either. The Thailand pages on the monger boards don't speak of them. If they do exist and they're like the operations in the Caribbean and South America, they're a rip off and completely unnecessary.
It doesn't work like you dream of for anyone involved. Instead you can go to the alley for a street girl, the clubs for a club girl or an escort for an escort girl. If you have the money you can hire a bunch for a week and sit in a suite and have as many as you'd like, as often as you'd like. Or you can order chicas a la carte as it is popular since time began.
Tijuana doesn't need such a all you can eat resort. Nor does it need to be a world class sex tourist destination. Tijuana just needs to keep being Tijuana.