Here's my Practical list:
Tsubaki, Jin, Ragna, Hazama, Hakumen, Arakune, Rachel, Litchi, Relius, Tager, Valk
Two groups within practical really:
1. Have to delay jbb to hit with jbb>jc (Jin, Tsub, Rag, Haz, Rachel)
2. Don't have to delay really to hit with jbb>jc, but if you don't have your timing down anyway then you won't combo with the following 5c, etc. (Tager, Relius, Litchi, Arakune, Hakumen, Valk)
Either group seems the same to me, should use the same timing for both I think.
Awkward?:
bang (feels like, jbb misses, or if jbb hits, jc doesn't combo or hits too high...)
Impossible?
lambda/mu (jbb hits, but jc doesn't have enough time to come out)
noel (jbb almost always just misses?)
Taokaka/Makoto (jb always misses for me, whether off 5bb or 5c)
Platinum
Carl (didn't test)
The other thing I'm wondering is how safe it is if you just do it until it drops. is that jC after it drops safe like a safe jump? Built in reset into that would be pretty damn nice...