Metahumans - how to blend control rigs during runtime?

In my project I animate the metahumans either with an Animation BP containing one ControlRig Node, with values that are provided from a cpp class, or with a LevelSequence with a baked control rig animation sequence.

My problem is that I would like to do both of those things (combine the values from the LevelSequence with those from the cpp class) simultaneously + other sources as well, like use the base animation from LevelSequence A (e.g. walking animation) and use the values from Pose B (e.g. hold a bag in the right hand) or Pose C (e.g. hold book in left hand) and some values from the cpp class (e.h. head look over there)

What is the best approach to do this during runtime? Either in cpp or with BP.

I tried in C++ to directly write the values e.g. from Pose C into the currently active UControlRig instance, but since that is not thread safe, unreal crashes reguarily - and adding thread guards, at least how I understood them, didn’t work, since the worker thread the evaulates the ControlRig didn’t care about them?

What I should add is, that at end I need exactly one Control Rig, that holds all the required information