At the moment creating animated skeletal controllers for AnimBlueprint is too complicated process in C ++, and existing controllers have very small and limited functionality.
It may make sense to create a blueprintable class (like the blueprint library), which can be added to the AnimGraph to the skeleton controller. Such as TwoBoneIK, SplineIK, ModifyBone and another.
Then it will be very simple:
created a new skeletal controller class in the library (C ++ or blueprints),
create function and input variables and write logic,
and you can use it in AnimGraph.
This would be very useful in my opinion.