hello BA !
do any one know how to slow up a parented object using python ? but insted of using all transforms in once use a Vector to control rotaions for example , so you have control to make the object slower on Z axis only but not other axis , got it ? it would be really helpful to have this script … come on programmers we need you !
Any one ? 
Normally as of having tried, modal operators, anim frame handlers, dummy drivers that sneakily operate on scene objects instead.
Right now the most predictable and safe bet would be ‘Animation Nodes’. Anything other than that seems very old school or hackish.
Even if you don’t like Animation Nodes, you can still write your own custom python and attach only that.