Lylat would be the main candidate in order to nerf Steve and Kazuya, and removing Kalos would help too. The former will be tricky to push since so many players dislike Lylat, the latter should be easier given that Kalos has so many issues (overlap with FD, timeouts being easier than on other stages, and it's really easy for Steve to drop anvils on Kalos compared to other stages, to name a few).
I've posted this a few times already but it's relevant and maybe some people didn't watch it yet so I might as well post it again:
In ordet to be ban worthy in a fighting game, it has to be really, really, really,
really strong. I recommend reading this:
https://www.sirlin.net/ptw-book/what-should-be-banned
Many of the things you mentioned aren't really used much by Steve-players. Will they be eventually? Who knows, but right they're not. Planking is not an issue right now. Meteor/hitstun cancelling doesn't seem to be as good as some people seem to think it is. "Slows games down substantially" is not even true, many Steve sets are quite fast. His OrionRank rating isn't
that impressive, Wolf had 780.25 points in 2019 (Snake at 715.5, Palutena 646).
Making the viewer experience worse I strongly disagree with. Many people, me included, think he's quite fun to watch, and regardless that's not a good reason to ban a character and it shouldn't be part of your argument when arguing for a ban. Right now, Steve isn't
close to being ban worthy. The concern is that he'll one day develop enough to be, but right now he's not close. If you look at other fighting game characters that were banned you'll see that they were way more dominant than Steve is right now.
All of this applies to Kazuya as well (and Sonic, ROB, or whoever else people might want to ban). Banning a character in a fighting game is quite difficult to do, for good reason. Steve is not close to being banworthy yet, and probably never will be (though "Steve gets buffed every 48 hours" could be an issue in the long term, hah).