The way i see all of this, the addition of hitstun will just brawlify this game even more... by which i mean noobify. Part of brawls, somewhat appeal, is the fact that every noob will react the exact same way to every attack situation and because of this you can win regardless of who you pick to play against them.
Hitstun is great in melee because the game is fast and so fast reactions are required to use the hitstun alotted. However, brawl is slower, and floatier as many have pointed out. Wavedashing makes the game 1000 times more fluent, so thank you for that, but if you also put in hitstun then you create a game that is slow and also doesn't allow you to react fast, at all, thus, in my view, screwing this game over even more!
no stale moves would be nice, and l canceling would be even better, but hitstun would really make this game SLOW... and no one wants it to be any slower! Leave brawl as a "read you like a book" game and improve on this nature rather than force the game to become a slower melee.