I had an idea to add to your b down "Slide Kick and Dive Kick" Idk if someone already told u this or if u just do not want to do it b/c i have not read through tha pages of this post. but maybe u can put tha B moves affect Like The Wave from his Suedoken (Im pretty sure i spelled it wrong) on Kirbys Kick and maybe make the kick a little stronger.
Its Just an idea. If you dont Like it. I apologize. If u do thats great and it would be a great addition to fighter kirby for your final renovation.

If U still Need an Idea For the Up Tilt, You Should use the ending animation of Captain falcons Raptor Boost. Just a Thought. and idk if u can or not but maybe u can add metal movement SFX like as if he picked up a metal box. Just a Thought. and idk if u were doing it or not but maybe u could make him heavier. cuzz ya kno spartans have that armour that ways like, a few tons or somethin. Just a Thought.....
You dont Have to Use any of this but im just trying to help b/c i really wanna see the finished product and play as MC.