Here is a list of the moves ideas I have that I think would make K. Rool worthy of an A ranking (since S is basically reserved for gimmick characters). Beware, wall of text incoming...
--Crown Toss: Would serve as a multi-hit boomerang, given its sharp spinning, dragging opponents either away or toward the Kremling King, depending on the time of contact. The crown toss could be chargeable, allowing the player to hold down the input to send the crown hurtling out further and further for more range, but at the risk of K. Rool remaining vulnerable, gawking at the screen here and there. The move could increase in speed as K. Rool takes damage, as in his boss fight.
--The Kredits: My pet Final Smash idea is for K. Rool to play dead, while the Kredits from his boss fight zoom up the screen, with their text serving as solid platforms that can carry opponents up to a Star KO like the Landmaster. The Kredits could be scattered around so that, even if a foe runs off the platform and tries to fastfall back to the stage, they may still land on more ascending Kredits. Alternatively, the Kredits could just hit opponents around, or could be attacked to send individual letters scattering around the stage as throwing items. From DKC, he also has Cannonball Barrage, but that may as well be called PK Cannonball, so yeah.
--Blunderbuss Balls: Could be taken in several directions. Regular chargeable cannonball projectiles could be fired, or spiked ones that deal additional damage and knockback. The most unique approach would be to allow either cannonball to fall to the ground after being fired, reusable as weapons like Wario's bike parts. The spiked ones in particular could serve as great team battle items, a bit like the Uniras. The player could also angle the trajectory of these projectiles, or even trace a path for them with the control stick while charging, allowing them to swirl around or bounce like in DKC2.
--Other Blunderbuss Projectiles: The blunderbuss is also capable shooting out barrels, which could contain any item in Smash context, as well as three different cloud varieties. Red clouds slow opponents' movement, bringing them down to K. Rool's sluggish speed, blue clouds freeze them, allowing him to charge up his slower attacks, and purple clouds reverse their controls for additional trickery. The blunderbuss can also serve as a Command Grab if its vacuum properties are used (this can also influence K. Rool's onstage projectiles), be used as a generic bludgeoning weapon, or as a rocket.
--Helicopter Pack: This is a relatively simplistic recovery move, though I have heard a number of suggestions as far as how it could work. Some say it could be used to give K. Rool "Dixie-esque" hovering, albeit with him falling a lot faster, others say he could gain multiple jumps from it before it sputters out. At times, you'll see people give it electrical properties as well.
--Electric Pods: Another pet idea of mine, here, K. Rool drops an electric pod to the ground, out of which a second pod extends in the direction of his choice until he stops it. From there, a thin barrier of electricity fires between the pods for a set period of time, allowing the otherwise combo-less K. Rool to juggle opponents off of it, or to camp from behind it, although he himself is vulnerable as well, and the pods can be attacked to disrupt the barrier. This is taken from his DKC3 boss fight.
--DK64 Stuff: K. Rool has his boxing gloves, which basically give him the vast majority of Little Mac's potential moves, and shockwave attacks, which could be used as a Down Special, a D-Smash or a D-Air and still function well. There's also his invisibility, which could be chargeable, or allowed in set bursts over intervals of time. And let's not forget a potential cinematic Blast-o-Matic Final Smash, either.
--Spinoff Stuff: K. Rool has spinning attacks, mine-throwing, various mechanical vehicles, and a Crystal Banana transformation from the Paon games, as well as a scepter from Sluggers, which, aside from generic bludgeoning, could feasibly be given magical properties.
--Miscellaneous: K. Rool has an entire army of Kremling troops from whom to borrow potential attacks, or even summon onto the field himself (namely the Kritters and Klap Traps as grunts). His crown projectile doesn't have to be limited to being a boomerang; it could be used as a disjointed projectile for other attacks as well, like maybe him tossing it up to juggle opponents. K. Rool has his golden gut for ramming attacks, also usable as potential super armor or a way to reflect projectiles, and a lengthy cape, capable of also reflecting projectiles, Mario-style, or even for slowing his descent from above, Batman-style. Realistic crocodile chomping, tail swiping and "the Death Rool" all fall under here as well, as do the various comical exaggerated moves or 'cheap' tricks he could pull. Hell, if you want a real stretch, he has 40 episodes worth of DKC cartoon under his belt which he can borrow attacks as well, like DK himself did.
So yeah, basically, piece any of that together, and you get a heavyweight whose playstyle emanates craziness, but with a strategic method to the madness, from tactical projectile use to trap placement to drawing in opponents and pouncing like a real crocodile. Kind of reflective of the guy himself. I believe this renders K. Rool easily worthy of an A placement.
EDIT: Oh, damn, how could I have forgotten the alternate costumes? Not saying I think this will ever happen, but if you make K. Rool a stance switching character between Kaptain and Baron, he could easily be an S character, beyond what I mentioned earlier. King would be a more well-rounded default state, while Kaptain would cost him his DKC speed and jumping for projectile prowess and Baron would weaken his attacks overall in exchange for more aerial dominance, courtesy of his helicopter pack. Throw in Boxer K. Rool, Pharaoh K. Rool, or even an all-new original Smash K. Rool if you want to spice things up more from there.