I've done this quite a bit myself, but it's more punishable than it may look. I'd suggest only doing it midscreen where the crossup has enough distance to get 2a to whiff. The main problem with doing it is that you commit and then you either have to do a low or the unblockable. (which in and of itself is not that bad of a mixup). I think the 623b unblockable is better than 5[c] because it's an untechable knockdown which you then get oki off of.
Can you mention few of the punishable things? I think you may be right in that regards to one has to commit to it. One thing I think that helps with the mix up is 421a/b.
But in the end Ryougi oki is the strongest when she cause a circuit break knock down from 6c,623c. While it does cost meter it limits some wake up options which some character dependent on I think.
Well, with 623b if you crossup there's just enough recovery for you to get hit by their 2a. If you end up in front of them, you will eat the 2a.
421b is the better of the two. 421a is slightly faster, but you can't jump cancel it, which is a huge downside. For a midscreen blockstring utilizing 421b (I'm assuming it's blocked) jump cancel and try to do a mixup coming down. Unfortunately, we lost the ability to cancel 421c into air normals so we can't do that absurd double crossup Shlopoke found in PS2.
I'd also like to point out that 421b's vacuum on hit has changed to a push. Makes it a little safer but makes oki off of a blocked one harder.
And unless it's meaty 421 loses to stuff like Kohaku 5b and Wara 2b. But it seems just barely safe on block. I think it's something like -4 on block, as you barely have enough time to block a 2a after you land and every time I do it I end up with a just guard.
The 421 and 623 series both have the downside that you have to commit to your choice. Once you do the input you can't do anything else until the attack comes out. But they look similar until 421 jumps so at least they'll have to guess which it is.
6c236c (This is what the input actually is, but it doesn't matter as long as the followup comes out.)
It does cut down on the options your opponent can use. But it's probably most effective on Nero as heat activation is his only decent reversal. I'm not really sure if it's this or 236c that is her best oki situation. The amount of time you have is about the same, maybe a bit more with 236c.