In terms of the new people, this is such a good crop. Sydney (villain potential), Leka (strong overall), Dee (crafty and competitive, also, not ugly), Tay (almost seems too nice for The Challenge, kinda like Horacio), America (reminds me of Corey in the sense that she seems to really appreciate being a part of The Challenge and grateful for the chance to be on TV), Adrienne (sneaky decent competitor), and Izzy (I don't mind watching attractive people on TV) are all female cast members that would be good to bring back.
Cedric, Yerami, Justin and Leo (tremendous wildcard weirdo potential) all seem like nobrainers to keep casting. Gabe has the physical side down and can probably figure out the rest with more seasons. Jake works as the nondescript Brit.
This is the best infusion of fresh meat that a) actually competes and b) isn't super annoying (LOOKING AT YOU, BIG BROTHER COHORT WITH JOSH, FESSY AND KAYCEE).