I think with a Smash Redesign, they'd ditch his flimsy superman halloween costume cape and go with something more like this
I base this on Dedede's Brawl redesign, which made him more regal and emperor-like.
Plus add some jewels to his crown and bracers, add some rings to his fingers. For extra goofiness, maybe make one of his back teeth gold. Make him more muscular, give him a more alligator like mouth (visible jaw muscles), tail and back fin/spikes. Make his wonky eye kind of lazy, have it not move properly when he emotes. Hunch him over a bit, play with him being hideous by design, but make it work and make it not seem so dated and 90s. Give him a roman armor skirt, or some kind of lower body armor to break up his huge green body. Give him longer and more muscular legs. Make his hand large and claw-like, add some webbing to them.
Make him feral like Wolf, with slashes and bites, but also make him goofy like Wario or Dedede.
Yes, this ignores stuff like Captain KRool, and his other appearances. No Blunderbuss, nothing like that. Ignore his 90s origins. Pretend he's a new character entirely, except for stuff like throwing his crown.
An obvious jab is his boxing from 64. Except don't do that. No, his jabs are now two slashes and a bite. What's a blunderbuss? No, this K Rool left that life behind. He's a new, modern croc.
Up Special: K. Rool Copter. Taking cues from his rival, DK sticks him arms and tail out and spins rapidly.
Neutral Special: Just kidding about the blunderbuss. Charges up a pirate gun and launches cannon balls. You could say this was cloned from Bowser Jr. But don't say that.
Side Special: Crown toss. He chucks his crown forward, pointy side first. Flies further when smash thrown, like super missiles or Mii's chakram.
Down Special: Klap Trap Toss: Puts down a klap trap (DK64 style) that walks back and forth. If it hits an enemy, it springs up and latches on and does damage over time until it's knocked off. Pikmin + Mecha-Koopa.
His normals are a mix of savage croc slashes, bites and tail slams. Combined with obnoxious body slams, punches, and stuff like tripping or accidentally rolling into people.
Avoid making him too goofy without losing who K. Rool is. Ignore stuff that makes no sense or is dated, leaving the memorable, timeless aspects of the character.
K Rool is going to be a big redesign they'll need to do to make it work. But I think it could work, and could work really well. It could potentially re-invent the character and bring him back if they do it right and try not to stick too much to the 90s. K Rool just isn't going to be able to be super accurate to himself, since himself is lame and outdated and desperately needs a redo.
