ability to pick single axis in Move Pivot

[Zemmu]

I'm not sure what you mean...the offset modes already have individual-axis pivot offset controls...

For example in "shape center" having individual-axis would be useful, but most of all in "Closest point to object". 
So for example I could line up all my pivots only on z based on a dummy. 
My workaround right now is using "Closest point to object" in surface mode and placing an horizontal plane below the particles (to align the Z), then another "move pivots" operator and a vertical plane (to align the Y).

in "Closest point to object: world" I'd like to pick a dummy, set the operator to "Target object location: pivot" and pick only the axis I want to alignt with target's pivot