I think that the step-dash discovered by MySmashCorner is very beneficial for Fox. He doesn't slide quite as far as MK or Bayonetta, but it's enough to benefit him.
https://youtu.be/KvRsb_2yE5Y
Some things about the step-dash:
- It is much easier to do it using the walk > (return to neutral) > walk > (return to neutral) + attack as shown in 1:08 in my opinion. The problem with getting used to doing it this way is that you have to use a move, thus it could make it predictable. When you crouch, you can react more accordingly.
- If you do it out of shield, make sure you just press shield and release; do not hold the shield button or you'll do a roll instead.
- Fox's step-dash distance is slightly more than his perfect pivot, barely enough to make a difference. The benefit over a perfect pivot is that he won't have to execute a turnaround out of this to face the opponent, which can be useful with his d-tilt, f-tilt, d-smash, u-smash and in some cases his u-tilt.
- Won't work with Fox's F-smash; like MK's, it halts Fox's momentum.
I've been theorizing the applications with Fox:
Edge-guarding
There are characters who can re-grab the ledge without much fear due to having aerials (Villagers U-air) or recoveries with hitboxes (MK) that go through the stage; using a step-dash > D-smash can help you stay in a safe position and punish the opponent when they try re-grabbing the ledge again.
Approach / Punishing
Fox's d-smash, u-smash, d-tilt and f-tilt can be used to start combos or push the opponent away respectively, and they can be done out of a step-dash to punish a whiffed move on reaction. You can theoretically also do a U-tilt out of a step dash if you do a turnaround right after; this is hard to do consistently though and a PP U-tilt would be sufficiently effective, but it is possible and I could see the benefit of learning this with the slight distance increase over a perfect pivot. As for U-smash, a JC U-smash is much easier to execute, but doesn't gain the slide distance of a step-dash.
Juggling
As shown with MK, the step-dash could help in flat stages such as FD when an opponent is trying to land. Because some characters have aerials that can keep them safe from Fox's U-air pressure (Cloud or Villager's D-air for ex), baiting this and keeping yourself slightly away from a landing opponent and then step-dashing in can give Fox a boost to punish their option with F-tilt, D-tilt (preferably the sweetspot), U-smash or D-smash.
I'd be interested to apply this myself in some serious matches. This isn't something you can learn overnight though, it's fairly difficult to do consistently. Hopefully someone here who is much more gifted than me and puts these applications to the test and posts more regarding this new tech; I think it's going to be crucial for Foxes to learn how to do it.