It's kind of a problem inherited from the MCU if that's going to be a focus from where they draw characters. Black Widow is probably the biggest name from there, Scarlet Witch is unlikely due to sort of being a mutant sometimes, and after that there's Gamora and... Sif? Extermis Pepper Potts, too. There's also Wasp, but her movie is a bit far away, still. Captain Marvel is already in.
Obviously if you take the comics into account, Ms. Marvel is a clear frontrunner, and Spider-Gwen as well as Gwenpool could be interesting picks, too. I wouldn't mind seeing She-Hulk return either.
But the problem comes from if you want most of the MCU Avengers + Ultron + Loki + Thanos, then you're filling up the Marvel side of the roster pretty fast. And not many of those will be female. To be honest, if they want to keep genders mostly balanced, the Capcom side might have to pick up the slack, if only because of the lack of approved options on the Marvel side.