Hello Guys,
So I have finally bumped into this issue most of you probably have bumped too.

Namingly:
I have this arm rig. Shoulder - Upperarm - Lowerarm - Wrist

Wrist is controlled by a Null named "IK_Controller"
Upperarm is IK driven
Lowerarm is IK driven too.
Shoulder is targeted to the null "IK_Controller" to establish a 2D plane in which the Upper and Lower arm can exist exclusively (otherwise the controller strays away)

BUT! When I switch to FK the Targeting from Shoulder to Wrist remains intact so I can't achieve a fully independent FK rotational solution. Whenever I move the target
it affects the Arm bones.

Is there any workaround for this or do I have to build my own IKFK blending system?
Thanks