You shouldn’t change the pivot at all. That’s the last your ‘resort’ and it should never be touched. Changing the pivot will make your life a lot harder in the long run. Instead you should build multiple layers of controls with zeroed out nulls.
In a skate rig, knowing the center of the borad is the main pivot and the tail the second and the nose the third for example, you would have a null located on each desired pivoting point. Than you should parent the board and each null to the main board null and after you should pose constrain the board to each pivoting null. Animating the blend of the constraints will give you much more control and a much more stable rig than changing the geo pivot.
Finnally you should have a couple more extra nulls on top of everything just for minor animation corrections.
Just be sure of making all the hierarchies (parenting) before you constrain.
I even made a quick test secne for you but it seems that we can’t upload different file types than images…damn…
Cheers.