I agree but he already got unholdables that's nothing new. Making that one useless ass punch I think it was 6P+K making that a CB won't be difficult. Making that useless 4P+K flying charge from 4 into a PB that would actually make it useful. Tengu stepping wouldn't be difficult either usually step moves are just moves taken from already existing moves. I can see his SS K being his spinning low kick and his SS P would probably be his P+K it would be awesome if it was his 2P. Balancing his frame data wouldn't be difficult either you would just need to change his stuff only by a couple frames nothing serious.
His frame data is easily one of the most important things that needs to be buffed. His jab should be i11, 8P should be a tad faster (maybe even just i14), and 8K needs to be at least i15 and launch on NH again. The vast majority of his remaining moves need to have the startup and recovery cut down by at least a few frames.
Another major issue is his inability to crush lows. He has no true way to crush a low. His best options are simply to low hold, or go for his 3T low OH. Both options leave him vulnerable to a Hi Counter Throw though.
He
does have three moves that crush lows; 7K, 7P, and 9P. None of these moves instantly crush though and the latter two aren't even attacks, though they do both have follow ups. All of those moves should instantly crush lows and H+K should be made to instantly crush lows as well.
I like your sidestep ideas. I don't think both of his SS attacks should be lows though (you suggested 2H+K and 2P). I like your idea of SSP being P+K though. I think SSP being 1P would be nice too, but this would be one of his many moves that needs to be faster. i21 is ridiculous. I would also love it if he could SS into 9P.
Speaking of that. 9PT should be an OH.
He also needs a huge reduction to the height requirement of his air throw. Basically, if he launches, his air throw should be guaranteed (same goes for Leon). 8P+K should also be guaranteed after launches again, and possibly be brought back to 50 damage.
Another issue is that his 7PP and 7KP need to guard break. In DOAD (don't know DOA4 frame data, but I doubt it changed much, if at all) they respectably leave him at -50 to -53 and -52 to -53 on block depending on range, and don't cause a guard break. What the fuck? Cut out a shit ton of those recovery frames and slap a guard break on that shit.
He also needs a lot more mix up options. Primarily mids. He's really lacking on those. He needs some new fast mids and his existing mids need to be faster.
He also needs better stuns. If I remember correctly, he only has one sitdown stun, which is the second hit of 1PP. I could see them making 3K cause a sitdown stun and then possibly add new moves that do so as well.
His special version of 2K, where he stomps on an opponent who's on the ground needs to be faster too. It is absolutely useless as it is in DOAD. His opponent can get back up before the move lands and punish him.