There's no one else to send besides Mariah and Bradie. Ting is the only one even remotely possible but it would be really silly to send her to Worlds as her first major senior competition. Mariah's results this season are respectable anyway. She's the clear #2. Everyone else is a complete nonfactor for the World's spot unless Mirai or Ashley actually make a comeback. Still, Mariah has had a good enough season to be sent to Worlds even if someone has a comeback and does well.
With all of this said, nationals surely won't be boring even with the lack of depth relative to other top countries. Bradie, Mariah, Ting, Alysa, Gracie, Karen, Angela, Megan, Starr, Mirai & Ashley (seems unlikely but still a fun thought) will all be interesting to watch for different reasons. Although I think the Worlds spots are a done deal (or at least should be), there are so many different narratives & storylines going into nationals, it'll be fun!