Gimmicks have been turning matches around for a while now..
None that matter really. However, the front low is great for the occasional surprise and offending your opponent's intelligence. Though it's gimmicky, I wouldn't say it's a total waste of an option. Front low is best if you suspect high shield or react to it if you're some kind of superman. It will make the opponent scared to try it.
The only real way to de-gimmick front low is to mix in jC fake land Ex-Bite, jC fake land 623c for jumps, and I don't know what for backdash(IAD jC?). All in all it's kind of ridiculous and relies on you being quite good at reads.
Anyways, as per the high mixups, I've finally finished my experiments with 496. They are a semi-success. The mixup itself is kind of gimmicky and the spacing is very finnicky. But if you implement it right it's pretty damn solid. Especially if you're not afraid to mixup the spacing on standard backdash jC. Say, adapting it for high airthrows. 4756 itself is kind of shitty and slow, and 496 off of high airthrows is almost the exact same speed as standard jC backdash making it great to mix in occasionally if you don't want to deal with 4756's shittiness. The best way by far to improve your 4way though is to alter the spacing on backdash jC with longer walkups and earlier backdashes or shorter walkups and later backdashes. The problem with 496 is that off of lower airthrows it can be extremely slow and easy to see. So unless you think your opponent is fucking terrified, you shouldn't risk it off a low one and stick with mid/high. What should be kept in mind is that at higher levels some people can block oki on reaction if you get stale, which is why you have to be tricky with spacing and options to put the fear of god into them. That fear is going to make them fuck up, and it's what you're really going to be depending on.
Why did I make this post? It's not going to help anyone, aside from Ultima maybe.