The FLUDD was an interesting utility in Brawl but... really that was it. A utility that took up a move slot that looked like it was headed for an amazing buff in brawl judging by the Luigi Cyclone. If the FLUDD were to come back (which, unless they have plans to change that soon, it is given the Sakurai vs translator battle), I'd like to it carry some extra usefulness given the situation Mario's in. For example, maybe if you use it while in the air, you gain the hover nozzle, or when you use it while running, you switch to the turbo nozzle.
Who knows, maybe the FLUDD was all a remnant from Brawl they plan on editing out later similar to Kirby's old midair Side B in Melee. Personally, I'd love to see his Down B become the spin attack from Super Mario Galaxy or the spin jump from Super Mario World.
Mario really is in for a buff regardless. Though the dojo proclaimed he was an all around balanced character, he was really a floaty character with an above average air game, short range, and bad recovery. I'd love to see him buffed since I loved the Mario Bros' air shenanigans in Brawl.