Animated axe asset - planning

I want to make a multi-purpose melee weapon, with multiple active modes.

I started with the base inspiration of an axe, and thought I could use a similar design to a Switch Axe from Monster Hunter.

I used this as a basis, but I wanted more than 2 modes, so I set about making a basic design.

Standard sword, long reaching weapon such as a pike or halberd, wide sweep weapon like a scythe and an axe.

My aim is to make a bone structure to animate the basic version, then I can make any design with the same structure and use the same animation.