Fix whatever causes the moves to sometimes trigger half-a-second after finishing your combo, add in grabs/throws, and you've got yourself a solid combat system for S4, in my opinion. Other improvements I'd like to see:
Move left/right evade to the bumpers or right analogue stick. Keep double-tap to move back if you have to, but man, double-tapping left/right to dodge on the same stick you use to move around the field is not great.
They need to come up a wider variety of AI to contend with. I shouldn't be able to spam one good kick over and over on Normal, but I did because it was effective.
And my God, remove the short-distance knee as one of your basic attacks. It feels so ineffectual and sloppy. If you want to just bash singular buttons, they should all be fast and effective moves, even if they don't do much damage.
The VF engine is a distant memory now. Even if SEGA handed it to YS for free...it doesn't work on modern hardware...it isn't compatible with a game built in UE4...it's just never gunna happen.