[Autumn]

You can already be pretty flexible kensei imo, we have options for daggers, fists, guns and bow katana that still allow you full access to kensei if you sub or main a sword katana with them.

All I could see you asking for is a 4 and 5* katana to get access to spear and axe katanas.

Or you could simply just ask for a Naginata instead of implementing a weapon for the sole use of mutation.