I know Sakurai is basically the "father" of Kirby, and that he knows what he's doing. Nevertheless, here are a list of changes I'd really like to see the day Brawl launches.
#1 Moderated Speed
Kirby can't keep up in speed, attacks, lag, and practically in every regard to any good character. To keep Kirby competitive, fix the big gap in speed between characters in mind. (as far as I know of Brawl, this problem is already being addressed).
#2 Kirby Hats
Give us the Kirby hats from his games! Mario, Yoshi, and Pikachu hats are cute, but instead of making a new hat for every character for every game and trying to balance out those attacks, just give him the expected list of Hats and you'll be set from Brawl and forever after.
#3 Fix Bad Attacks
I don't care if an attack isn't uber, godly, or even especially spammy. What it needs is a reliable use. Kirby has too many attacks that just aren't useful in any practical sense. Many people would point at Stone, Hammer, and even the Final Cutter as the most obvious culprits, but instead of buffing these attacks they should be changed to something completely different and those attacks should be integrated into Stone, Hammer, and Cutter hats.
#4 Swallow, Copy, & Star Shot
Copying is Kirby's shtick, his singular trait, the attack he should be best known for. Making Swallow and Copy a reliable and useful attack would give players reason to use it. The main problem with it now is the terrible startup and horrible lag, all for an attack that does 8% damage, sets up the opponent to hit Kirby, and really doesn't give him any useful ability most of the time.
I realize that if Swallow had a great reach, grab priority, and little lag, it could be spammed and pretty annoying to the opponents. First of all, this really isn't such a bad thing as it would give Kirby at least
one abusable attack. However, with the inclusion of "Swallowcide", this becomes more important to balance. The obvious thing to do is to improve Copy, and make Swallowcides harder. It's easy to do this: make it so opponents can break out very quickly after getting Swallowed, but make Copying fast and easy to do. If you're going to make Swallow like a grab, give it grab-like lag and range.
Star Shot is another shtick of Kirby, but what use is it when grabbing is easier and deals about the same damage? Well, the obvious thing to do is to improve Star Shot so it's more on par with Kirby's Throws. The amount of damage should be slightly higher, say 14% to 18% based on weight instead of, what, 10% to 18%? And pick up the speed on that thing, it seems to take forever to grab someone with Swallow and spit them out at a nearby opponent.
And, finally, give it some KO power. If Kirby's U-throw can kill someone approximately 200%, surely Star Shot could be used for KO potential. Just make "breaking out" of the star harder the higher percent the opponent has so that if they can't break out before being sent off-screen they get KO'd.
#5 Combos
The fun of this game is stringing attacks together and pummeling your opponent(s). Please give Kirby some combos. Kthnx.
#6 Hat Examples
Beam
Standard - Laser (like Fox's)
Side - Cycle Beam
Down - Beam Whip
Up - Beam whip (tether recovery like Ivysaur's)
Sword
Standard - Non-Stop Cutter Attack
Side - Cutter Boomarang
Down - High Speed Cutter Drop
Up - Final Cutter
Fire
Standard - Fire Blow
Side - Burning Attack
Down - Fireball Roll
Up - Fireball Spin
Fighter
Standard - Energy Ball
Side - Spin Kick
Down - Sweep Kick
Up - Rising Break
Hammer
Standard - Hammer Nail
Side - Hammer Swing
Down - Hammer Flip
Up - Giant Swing
Ice
Standard - Freezer Breath
Side - Freezer Blizzard
Down - Ice Kick
Up - Freezer Sprinkle
Parasol
Standard - Parasol Shield
Side - Parasol Drill
Down - Parasol Dive
Up - Parasol Chute
No Good
Gives no Hat
Bowser - Fire
Charizard - Fire
Diddy Kong - Fighter
Donkey Kong - Fighter
Fox - Beam (Laser)
Ice Climbers - Ice
Ike - Sword
Ivysaur - Fighter
King Dedede - Hammer
Kirby - No Good
Link - Sword
Lucas - Fighter (Yo-yo)
Mario - Fighter
Meta Knight - Sword
Peach - Parasol
Pikachu - Beam (Spark)
Pit - Sword (Cupid)
Samus - Beam
Snake - Fighter
Sonic - Fighter (Wheel)
Squirtle - Fighter (Bubble)
Wario - Fighter
Yoshi - No Good
Zelda - Fighter (Mirror)
Shiek - Fighter (Ninja)
Zero Suit Samus - Beam
The Hats in parentheses are additional hats they could add specifically for those characters.