Dedede is a zoning character at heart. He aims to keep people out, and once they get in he wants to try and land a grab to send them back out. Also I can't help but feel his game should focus on stage control with waddles. I've always wanted the ability in regular Brawl to just set one in front of me, rather than tossing.
Also I'd love to lose the gordos, but in return
Waddle Dees no longer have their "nothing" actions (like the trip and look about and such) in their options and always do one of the three jump attacks, thus actually mattering and giving me a reason to want them out
Doos unchanged, maybe make the lasers a little easier to SDI but not too much. Maybe tone the damage down a little, though definitely not too much or you'd ruin them.
The ability to choose between the two. Like... an outward angled throw fires a Dee and a neutral angled throws a Doo? Possibly with the downward angled variations throwing them straight down in front of Dedede, so that they can be set in front of him?
Also if you could make inhale not eat them, that'd be the icing on the cake.