How to animate the mesh on any axis?

Hi everyone , I’m a freshman of babylon.js .
I have a question and I hope someone can help me .

My playground:

It is an easy way to make it rotation from aixs with animation (upward to any axis).

or like this? rotate from any axis?

Why not modify the quaternion directly?

quaternion is not linear, if you want to control it by animation, it is hard to set keys

quaternion animations are slerp so it should be ok.