Hmm, the Bath Within gives her a quick animation, and basically turns her dodges to being better than other dodges by a few frames. Reflex says 13+ frames off of her normal animations, but consider that her normal animations are crap. So long lasting hitboxes, or multiple hitbox attacks, can be good to punish this, especially since apparently activating Bat Within slows down your animation! I didn't know that part. Someone mentioned a well placed Luigi Dsmash will do the BW damage and hit the later part, effectively punishing the roll even more than a normal hit.
Now the question is, what level of control does the Bayonetta have? Can she alter where she ends up with directional inputs, or is it determined when the BW activates? I personally think it is the latter, in my games I can never get it to do anything besides end up where it would normally be, but I admittedly haven't done any specific testing with it.
She still has a slow grab and jab, so again her best option post BW is the Witch Twist. So basically if button press speed is ever a concern, such as if you break her zone, be prepared for a Witch Twist.
Also, she can SHAD -> Divekick, an interesting mixup I thought of on the bayonetta boards, someone else (i believe pikazz) confirms it works to get the hitbox out, and can bounce off of shields. I bring this up because I think it is these kinds of things we are going to see happening to her meta, I don't believe her punish game will get more fleshed out. People will learn optimal setups for no DI (where they kill usually) and optimal setups for DIing opponents, one will emerge with max damage for each situation, and they will be used. Her combo game is incredible, but it isn't totally fluid in a way that really makes me think much more will grow a great amount. This is mainly due to the way her specials work, they were clearly made to be combo moves, and they work, but often they are the only possible followup. People will discover that a uair here is better, or a Witch Twist into Witch Twist is more optimal/sets up a kill 5050 earlier, but the combos aren't going to get longer. Really they should get shorter as people learn to SDI.
Another CQC option she has is landing dair. If she starts the dair, the frame she hits the ground there will be a hitbox, even if she dair'd the frame before. This is similar to pika's landing dair, and I think many others, and will serve similar purpose. It can be a quick f1 combo break, but only in situations where you are forced onto the ground. This is nice for mixing in against characters that like to do something like jab you, let you mash AD, and then punish you for falling onto the ground during the airdodge, but most combos have nothing to fear from dair.
I bring these up as CQC options are integral to the efficacy of Bat Within, these are some options you will see before and after her dodges.
The slowing of enemy animations might actually prove to hurt her, as extending hurtboxes in duration might make some moves able to punish BW even if they don't have 20 active frames.