I don't normally make posts of the forum but because this is really personal I can't help but get involved somehow. I'm a long time fan of samurai, if it weren't for my interest in sage and a few other jobs it would certainly be my main job. However, if kaiten gets removed I don't think I will ever return to the job. It won't be satisfying anymore.

Samurai's core identity to me:
Flashy and epic sword animations/sound effects.
Big damage and good combos (that feel good to pull off)

I believe that removing kaiten would for one make the job less enjoyable. The satisfaction of knowing that my midare is going to be big thanks to my input, feels great. Knowing that my higanbana is going to be the best it will ever be once I use kaiten feels great. I like working for that damage boost, and having such a cool ability makes it even better. Simply making them crit or increasing potency for the loss is ridiculous. (Side note that I main sage, and I love eukrasia. I love hitting oGCDs that modify my skills or increase their potency, much like MCH.)

What I would suggest if your problem is just "button bloat":
Remove tsubame-gaeshi as a hotbar button and make it executable after Iaijutsu on the same button. I know this is doable, and it's really weird to have it on a different button anyway. Make it so we just double press the same button and it would alleviate "button bloat".

I personally do not have a button bloat issue with samurai, and even the suggestion that it does makes me laugh. I could see it, but the job works as is. The only issue I have with button bloat would be easily fixed with the suggestion above.