How to pickup a "physical" weapon which has collosion, and animating the pickup action, while upper body is Ragdoll?

If you picked it up, it should be attached to the parent actor. In the overlap method you can check if the weapon collides with the current parent actor and ignore that collision by just doing nothing. Otherwise all overlaps and collisions will react like you want it to.

There might be some other ways to solve it, but that’s a pretty forward way to handle it.