This. I've totally believed this for years. Hell, I believe we might have gotten all the Forbidden 7 if Brawl had DLC.
Honestly, considering how Smash 3DS/Wii U and Ultimate went, here's what I think Brawl DLC would've looked like.
Dixie Kong goes first, mostly because of her Semi-Clone Status.
Terry goes Second. Mostly due to this being the First Smash Game with Third Parties. I'm mixed on whether Mega Man would make it or not. If he were to have made it in, then I think Mega Man would've been in the Second Half.
Mewtwo is in the Middle.
Krystal would've been right after and would've brought along Classic Costumes for the Rest of the Star Fox Characters.
Not sure if Mega Man would've made it, but if he was prioritized, then he would go here.
And SEGA would've probably forced the Werehog in because SEGA likes Money.
As for Stages, I think Terry, The Werehog, and Mega Man if he got prioritized would've come with Stages, probably KOF Stadium (the Cameos are still a thing here in order to Reuse the Trophy Models), Rooftop Run for the Werehog, and Wily Castle (without the Yellow Devil) for Mega Man. I think Fountain of Dreams, Flat Zone, Saffron City, Kongo Jungle (64), and Hyrule Castle would've been brought back, on top of Mario Galaxy probably getting a Stage as well. And all the DLC Stages wouldn't have any repeating Tracks. This would've been before that Philosophy Shift within the Smash Team. I'd imagine Kongo Jungle would've gotten DKC 1-3 Music, Saffron City would've gotten Some Gen 3 Music, Fountain of Dreams would've likely gotten some Kirby Air Ride Music, Flat Zone is an exception, mostly because of how Limited the Music Selection is, and Hyrule Castle would've likely received some Ocarina and Majora's Rips. Mario Galaxy would've probably had Seven or so Galaxy Rips, and it's pretty obvious what the Thrid Parties would've received. Also, PM would've been in a weird position lol.