I can picture this move giving some characters an advantage over others simply based on the nature of their up-b. Someone doing this to their opponent could easily set them up for being hit with their opponent's up-b. Characters with an up-b that hits above them and is fast enough will have a significant advantage over those that don't. Taking Melee's hitboxes as a reference point, someone like Peach or Marth, who can use their up-b to hit someone who is above them will have an advantage over someone like Captain Falcon or Ganondorf, whose up-b hitboxes are to their side instead of above, unless the opponent ends up on their side after the meteor cancel. Someone like Jigglypuff or Kirby would have to use a jump to meteor cancel it, but might still be in position to do a b-air if doing a footstool jump lags the opponent. Mewtwo and Zelda would be able to teleport to safety, but not necessarily be able to punish the attempt. And Ness is screwed (thunder eating).
Also, there are a few other aspects of this which we won't know until the game comes out, and will affect the usefulness of this technique.
1. How precise is the timing? Is it like teching, or like powershielding? If it's like teching, everyone would do it if it proves to be useful. If it's like powershielding, people who do it and can utilize it in a real match will be a lot rarer.
2. How much will it lag? Both the jumper, and the jumpee. If it lags the jumper too much, it might not be worth doing often. If it lags the jumpee too much, there is potential for dumb infinites such as fsing the opponent over and over with them being unable to do anything about it.
3. Will it do damage to the opponent? If so, is it the same amount for everyone, or relative to their weight (Bowser doing more damage than Kirby, for example)? If it doesn't damage the opponent, it'd probably be better left as an Easter egg and a surprise meteor on noobs. If it does damage relative to weight, it'd give heavy characters an advantage which combined with other factors could help balance out their slowness.
4. How much knockback and stun will it do to the opponent? Is this a set amount for everyone, or relative to weight and/or damage dealt? Something that damages and stuns similarly to Ganondorf's d-air is obviously more useful than something similar to Zelda's d-air.