I think that your point about him having very different levels of balance among match ups due to the nature of Ice Clone, is very true. However throwing out statements that he had many 7-3 match ups which is very untrue and seems like an arbitrary number you've attached to support your statements, which you really didn't need to because you were already correct.
Ice Clone IS a unique tool, and it will be hard to balance every character to play in a game with it, and it think we just have to accept SZ is going to have a hard time sometimes. He is going to have varied match ups, so when discussing balancing him, it's better to aim for just him to have some weak matches and some balanced ones, rather than making a BUNCH of characters have bad match ups against him, all to accommodate the unique tool he brings to the game.
That being said, I think they actually did an excellent job of balancing him this time around. He's solid mid tier, with no real stomps, he has tools to get him through any terrible match ups that might arise anyway, there is only so bad you can be with a solid 50/50 and a 37% HKD wall combo (into the reliable threat of 50% off either 50/50 if they have no meter/armoured wake up), the ability to carry characters over there from connecting just about anything at all from absolutely anywhere on the screen, (and still getting close off things that don't quite make it all the way to corner from centre screen like raw clone/Iceball), a really good back and forward dash and run speed, great JiP / NJP, two very useful armoured Wake Up (one that both AA's and launches from the ground and is a small combo starter with good carry or corner swap off F42 into either Slide or Grab respectively, and one that hits low with immediate position switch all 3 of which leaving no teachable knockdown) , a 7 frame punish into full combo meterless, and even the Clone which is always SOMEWHAT useful even against Dvorah (sure she has tools to get around it, but just the threat of the clone wards the ones that don't), these are all very solid tools even if they aren't ridiculous, so that it's really hard to give him a "terrible" match up other than by putting an OP character in front of him, which is an issue with THEM that needs to be fixed, not an issue with Sub.
Also, while saying "play something else!" is usually a poor excuse for balancing issues, I think given the nature of Ice Clones varied effectiveness in different match ups and how this will ALWAYS be the case, it's fair to point out that if you really feel Clone adds too little to a specific match up, that Cryomancer is a very playable variation that actually lives up to the term "variation" as it really throws some new tools his way that can tear holes through Dvorahs defence, and make a match end a lot quicker, and Unbreakable which trades off Ice Burst wake up, for a zero chip mechanic, and a freeze that DOES work the only place that clone doesn't in this match up, against extended limbs, if this is why you think Clone is useless here. Somehow I think you'll find the Clone is still more useful against them though, that tool has many uses.
I don't think fixing the Clone hitbox will make him OP or anything I think something needs to happen here to make it do it's role, however he doesn't need any other buffs that would throw out currently balanced match up, he's fine as is.
