There's 19 Women on the main roster minus Charlotte, Alexa, and Nikki Bella, though I also assume they will have have Charlotte and Alexa in there on the stipulation they can challenge for the other brands title if they win. You have to think 1, if not both of the Bella's will be back, even if it's just a 1 off return for a Total Bella's/Total Divas storyline.
So let's say 22 Women right there.
Billie Kay, Ember Moon, Peyton Royce, Kairi Sane, and Nikki Cross all can make appearences.
So that's 27.
I assume they will bring back some surprise entrants to fill some spots, reducing the amount of NXT women needed, Trish said she wanted in, Lita probably could, maybe Beth Pheonix, we know Rousey will probably be in (in fact, probably all 4 of the UFC Horsewomen?
There will be more than enough I think.
Bigger issue is time. You're looking at at least 1 hour 45 minutes for both of the Rumble matches