I already talked about what buffs K. Rool needs in another thread, but in short:
1. K. Rool needs better shield pressure. Too many of his moves are unsafe on shields and he really struggles to threaten shield breaks with his attacks usually barely scratching shields (minus Down Smash, but that's punishable). Forward Smash is especially laughable here considering its speed and fellow heavy weight's forward smashes. Seriously, which other heavy weight is almost completely countered by shields?
2. Kannonball needs to not lose against so many things. Slow and non-spammable projectile losing to faster and spammable projectiles is just bad, not to mention that laughable shield damage.
3. Similarly, Up Smash should have higher shield damage on the last/prelast hit. Make it a "i cover a lot of options move" like it looks (cover above and in front of you).
4. Allow
to use Krown more as a setup or bait by reducing its downsides (it shouldn't be that bad to lose it). Completely cancelable pickin up animation would be cool too.
5. Make him better at approaching, as his moveset points to him being "pressure, bait and punish" character, and you need to get to your opponent between "bait" and "punish part" to do that.
6. General frame data improvement, most notably on Nair, Krown, Up Smash and maybe some other things.
As for things others said, i kind of don't like
KingDoop
's idea of having higher damage with Krown on. As nice as that concept is, it would be another reason to not use side b, so unless they fix Krown's issuess, i dont think that's a good idea.
Also, a big nono from me on Blunderbuss being a reflector as well. It would make more sense lorewise to make him blow up after that... and we don't want that. Also, we already have a reflector, and assuming Down B gets buffed, i see no reason to give
another. And even if it doesn't... nah, just no.