But you're not ... you're not really in danger while you're air blocking. And certainly not while you're in the corner. If you're air blocking a bunch of hits against Tian with your back to the wall, there's basically nothing she can do to you until you land. She can't make you guess between high/low in the air, and she can't make you guess between left/right in the corner. Most attacks seem to put you into aerial blockstun until you land anyway, so air-to-air tick throws would be very limited, and difficult for Tian to set up, and extremely telegraphed.
Remember: you have to land at some point. Also remember that your blockstun doesn't carry over when you land, so as soon as you touch the floor, you can do any of your grounded reversal options anyway. Backdash is free on everybody, and can work even better when you're cornered if you avoid the right move (free punish, since you're still in their face).
Getting caught air blocking, especially in the corner, is completely free and effortless. Once you're in aerial blockstun with your back to the wall, you are just literally immune to absolutely everything, almost always all the way to the floor, which creates an automatic gap in their pressure no matter what. In terms of defense, you cannot possibly be in a better position than that.
This is why I'm confused by this discussion. I don't say this to be mean or sarcastic, I just genuinely cannot understand looking at the absolute best possible defensive position that's even imaginable [Immune to high/low, immune to left/right, immune to ground throws, 90% immune to air throws, which are techable on reaction anyway, with a guaranteed pressure gap the moment you're vulnerable to anything, and you can still pushblock], and then being disappointed about not having an expensive and risky redundancy.
Like, from where I'm standing, I'm right there with you on: "I can't see any argument that aerial Cross Canter would be OP", because I can't even see why it would ever be good for anything in the first place. The purpose of Cross Canter is to forcibly create a gap in your opponent's blockstring, but landing from air blockstun just does that for free, and you're pretty much just completely safe until you get to that free gap anyway, and you have a broader variety of options when you get to the gap. Options that include "Continue blocking, and do a ground Cross Canter", by the way.