Gouie deserves an airdash, and giving him a wavedash that can be held to become side-special 2 on the ground would also be cool.
Worried this might become broken? It’s also easy to tune, with a bunch of potential different options to vary its function slightly: Make it only cancellable by aerials, or other specials, or by neutral moves (jab, nair, suck). If that limits the creativity too much, make it only cancellable on-miss, so if you make the wrong timing read the opponent’s only hit with the side-special hitbox; or make the window short and at the end of the dash, so it’s not as quick, but still a burst option that extends his meaningful threat-range.
As for gameplan and matchup effects: It would create an actual side-special 1 versus side-special 2 mixup in neutral, so the second side special’s attack cancel can see some limelight. Since Gouie would have a quick burst option, I’m also hoping it would cause swordies to have to approach more in the matchup, since their defensive zoning would be less effective.

There’s no reason to make this character any better

SideB1 just feels terrible to use because of how much endlag it has, i wish it had some on-hit cancel like Maypul has

On-hit would be fine, probably