I posted something about this in the LD last night. Charlotte vs. Rousey as so much more appeal than Bliss vs. Rousey, but I can't just see them putting her on Smackdown. They always put their biggest draws and special attractions on RAW, and Rousey is the epitome of a huge draw and great attraction.
Maybe they can have her appear on both shows until she makes a decision on who she wants to face sometime in March but I don't know what her schedule is like with her movie or if that's even doable.
Something that they COULD DO is... they could put the RAW Women's Championship on either Asuka or Rousey before Mania and have Asuka/Rousey be the match at Mania. (Asuka slapping Rousey's hand away probably didn't happen for no reason). IF they went that route, I think it'd be more likely for Rousey to get the belt. There would be a precedent for Asuka asking for her match before WrestleMania, I know Cena did it in 2008... and I'm pretty sure it happened a time or two before that as well. But I think the chances of that happening are slim considering that since this is uncharted territory for the women, they probably want the Rumble winner to go the traditional route to WrestleMania and challenge the champion.
Look at these Ultralight Beams flowin'