The thought of WWE keeping Asuka out of the first ever female Royal Rumble in company history may irritate some fans, but it'd preserve the Japanese wonder woman's unbeaten streak. The writers should run with a Raw Women's Title win for Asuka over Alexa Bliss (probably on the Rumble pre-show) and then sit her at ringside to see who will challenge at WrestleMania instead.
Both options are open, and a win over Bliss is the best course of action if WWE want to maintain some of Asuka's lustre during 'Mania season. If she's in the Rumble, there's no guarantee that she'll win anyway. Look at the first ever female Money in the Bank match as proof of WWE's dedication to shocks.
Just as Carmella's win deflated the audience hoping for a Charlotte Flair victory then, seeing Asuka dumped out of the Rumble would leave her in the same limbo fellow countryman Shinsuke Nakamura finds himself on over on the male side now.