Not really sure that's a great idea. Just because you've conquered a certain weight class, doesn't mean your body type can translate well into higher weight classes. Look at Roy Jones from LW to HW. Sure, he could beat Ortiz...but Ortiz was one of the weaker champions the HW div had seen, at the time, and Jones was in that div just long enough to win one fight. After he dropped back down to his natural weight class (where he had dominated for years) he lost a great deal of muscle structure/mass, and just couldn't regain it. To me, it looks like bantam is her most natural weight (if not a tad lighter), I'm not sure more weight would fit on her frame as well as her current class.
Plus, it's not her problem if she's murdered the division, it's the UFC's problem for not finding her worthy competition.
The big difference is Roy Jones Jr started at Welterweight where he dominated and continuously moved up until he made it to Heavyweight. Not many fighters can make that jump successfully. Also when he moved back down in weight it was more age that slowed him than anything else. Plus with all the trash she's been talking about beating guys in way higher weight classes maybe she needs to prove she can beat dominate at the next class up. I mean when Anderson Silva was dominating Middleweight everyone wanted him to move up to fight Jon Jones or even fight GSP at a catch weight. Then GSP took time off, Jon Jones has been suspended indefinitely and Silva lost twice.
Ronda could move up if she wanted but then she would be in the same weight class as cyborg ,who she's been ducking for a while. But there are plenty women fighters at higher weight classes that UFC could bring in from their other promotions. They won't do it because no one would be interested in Bantamweight once Ronda left as she's squashed them all.
Age wasn't the only factor with Jones, Pre-HW Roy Jones muscle structure was much different than post-HW muscle structure. Take a look at the pictures of him in his first fight after he moved back down, and a picture of him before he moved up. There are clear differences in his build, at that point. You also, cannot directly compare weight classes in boxing to MMA (I pointed out Jones Jr. as an example of why moving up can be detrimental, not directly comparing the two, at least, that wasn't my intention). Boxer's can lose all kinds of muscle mass in their legs, and it doesn't matter in the slightest, because they don't have to deal with leg kicks, leg bars, tosses, wrestling etc... MMA fighters do.
And if you hadn't noticed, Rousey has actually moved DOWN in class, since her Judo competitions. It's entirely possible she realized she needed different weight distribution to fight MMA versus strictly Judo? Just a guess, no real proof of that.
You can say she's 'ducking' her, but yeah, kinda hard to 'duck' people who aren't in your division, at a weight you've never competed at in MMA before. Funny how the same isn't being said of Roidborg.