Becky Lynch is lightning in a bottle the likes of which the WWE hasn't had in a really long time. I was dismissive of the Austin comparisons at first, but I've come to the conclusion they should just roll with it and see how far it takes them. She's light years better on the microphone than anyone else in the women's division, works a good match (she isn't the best female worker, but she's still incredibly competent), and is completely owning this "I'm taking what's mine and not taking crap from anyone" character that made Austin a superstar in the late-90s.
Honestly, the next move I'd make is to get Stephanie McMahon involved in her storyline and just run Austin-McMahon but with female participants. Maybe you write it as Steph deciding to name herself "Head of the WWE Women's Division" (since Evolution was such a rousing success) and deciding that Becky needs to be brought to heel. Maybe you position the Bellas as her "muscle" and draw heat with them being Stephanie's ideal for the Women's division, given their look, crossover success and in-ring success.
Make Stephanie the ultimate mean-girl boss and let Becky play out everyone's dream of being able to just smack the taste out of said-boss's mouth. It's what made Austin-McMahon work, and there's absolutely no reason it wouldn't be massive this go around as long as Steph is willing to bump a bit and let Becky get the upper hand in the end. You work to a 2019 WM match that includes some component of Becky v. Steph.
Meanwhile, you transition Rousey to a heel and have her align with her friends to form an former-MMA women stable. Your 2 year build is to a WM in 2020 that is headlined by an NXT 4 Horsewomen v. MMA 4 Horsewomen feud, with the main event being Becky v. Rousey.