If I were re developing momiji with the changes I thought of I would do this.
Izuna from a raw and hold-
Momiji is definitely and now more so a stun launch character, with the properties that the Izuna hayabusa has with the punishing of holds he can most definitely get the Izuna or juggle. Momiji being able to extent her combos using her uzakaze stance variants would be able to have a another tool from neutral to get her offensive game started. It would make other players respect her up close and not try to rush her down. I see this in a lot of people who fight Momiji they rush her down and Momiji is left to stay on block to wait to get the back to mid range for her to be come back on the offensive(effectively). I would however not give her the same damage output as hayabusa, he has had years to master that craft, Momiji only made her own variant. I would mak the grab these inputs and stats.
Raw Izuna- 63214T~82T or 63214T~41236
Frame 15(2)18 Dmg-99 NC-115 HC-135
Same input for the hold variant( maybe a adv. highP or change the adv.MidP)
Frame 18(1)31
Low-string variants-
anyone that plays Momiji or fight against her has a 66% chance of holding any of her strings and moves because most of them are Highs and Mids. Her lows are great! I personally use her 2H+K and 2K a lot. Up close I would like to have the option to get advantage on my opponent when they block my obvious PPP or PPK. Her tenku hop on block is terrible because she is not actually at the advantage the training screen shows but only her follow ups. I am well aware that you can always free cancel but who is to say your opponent won't strike punish you and put you into a mix-up when you tried to go for say 2H+K or 1P and they punish you with a mid because you are -8. With the incorporation of a low it will allow the pressure to stay on the opponent while Momiji is close. I think 1 or 2 Punch and or kick string based lows is appropriate something along the lines of say
PPP2K or K2H+K
Frames for 1st string- 10(1)12-6(1)16-16(1)22-15(2)24
Frames for 2nd- 12(2)15-22(3)28
Tenku T ceiling hit-
this is and if anything,the move I think she should have. All the ninjas have a ceiling hit move that allows for a launch combo and or power blow set up, which Momiji lacks except, for her ceiling Izuna. First, Momiji thrust her opponents into the air just one character space shy of a power launcher, with this being said she should well be able to use all of her strength to hit an opponent on the ceiling, this addition would play an essential role in her ceiling game in conjunction with her Izuna, while also giving her the option to do a launch -juggle.
I am not sure of the frames on this one
Also she should be able to do her Izuna variant off cliffs like hayabusa, like he does on lost world or any other place that has cliffs. Momiji does this on danger zone In scrabble, is it so far fetched to have it off cliffs as well, Momiji and hayabusa's izunas are relatively the same thing just different animations.
I am in no way shape or form the best Momiji player but I have been playing her since doa5u and these are things I personally think would give her the tools to combat someone like Helena, Rachel, Ayane or Christie. She can hold her own don't get me wrong I have done it plenty of times it is just I feel she needs something to boost her up. She is just a great underrated character.
"Better luck next time, huh" -Momiji