Carmouche has the best chance. There's no one at flyweight who has anything like Nunes' standup, and certainly not her power & timing. There's a bunch of grapplers who could potentially give Shevchenko problems on the ground, but they're all slow and/or unathletic with dogshit standup, they'd get stuck on the outside and get outpointed or blow all their energy trying to take her down like Pena did and then get finished or outpointed.
Carmouche is likely the strongest and one of the fastest fighters at 125, and though her technique could use some work she's got fast & hard takedowns that aren't easy to stop along with a decent ground control game. With the right game plan and some luck, Carmouche can pull off a lay & pray win.