Coming from a person who used to be a big supporter for MAD and thought it was vital to Brawl+, I think it should take a sideline seat.
My reasons are:
1) Wavedashing is faster for almost every character over dashing, and obviously over walking. When you can consistently stack WDs (and trust me, its not difficult at all), why would we ever use dashing or walking, especially as its basically walking at a faster speed. It's not that other forms of movement would be lessened, they would be almost nullified. We're choosing not to use it that way because we're used to Melee WD, but if we keep MAD dashing and walking is useless.
2) No lag frames on landing. I don't quite get how this is a good thing. Have you seen WD Spot Dodge approaches? No seriously, in the hands of a human player who knows how to utilize it effectively, the WaveDodge is among the best approach techniques out there, but in an overpowered way instead of good. Don't we want to add depth to the game while maintaining what we already had?
3) Coding room. Enough said. MAD takes up a third of our coding space, and with ALC, hitstun, and no tripping, thats well over half the memory we have.
4) It's completely unnecessary. Hitstun, LC, and no tripping are necessary parts to Brawl+, because they are the things that make combos possible. What does MAD do except override any other movement options with a superior, overwhelmingly easy and broken technique? Sure, you can Wavesmash or Wgrab again, but we have those things in Brawl already without ease: walking or shield grabs, respectively. Once again, don't we want to add more skill and depth rather than removing some?
Anyways, there's my rant. I think the bottom line is that the line MAD-supporters use of "MAD adds new depth into the game" is actually completely null. Sure, it adds the ability to slide around the stage and use whichever moves you wish with basically no consequence due to waveshielding or wavedodging, but we also take away the art of approaches, using specific methods to perform moves (walking/shielding out of a dash to do a smash) in situations, which, in my opinion, requires more skill to know and utilize then simply WD'ing into anything.
EDIT: KayJay, that code is going to be made.