If they ever actually go through with this, I still think between Austin and San Antonio makes the most sense. Put there, the resort would be served by two major cities and international airports. From there, further easy access to two heavily traveled interstate highways (I-35 and I-10). If built out where the resort would be more closely accessed by the 130 toll and you nearly have a copy of Orlando. Further, it puts the resort within a six hour drive of the major cities in Texas, western Louisiana, Oklahoma City, and northern Mexico.
It would need to be a third castle park, or something similar in scale, to have the right amount of pull to the destination. Even if they just built a castle park with the unique variations of rides that have been built in the international parks (especially as I don't see the park in Texas having as much of an international pull from European and Asian markets), that would make the park a must visit location for locals and WDW/Disneyland visitors alike. Pretty easy to put together - Adventureland like Hong Kong or Shanghai's Pirates and Adventure Isle, Frontierland like Grizzly Gulch, Phantom Manor, etc, Fantasyland with Fantasy Springs rides or Beauty and the Beast from Tokyo Disneyland, etc. All known quantities that work, all similar enough but unique from what is offered in the other stateside parks. Would seem to be the appropriate release valve for the crowds they are seeing in CA and FL.