Calling System Library BP Nodes from custom BP Class

I have created a new BP class derived from Object. I don’t need all the overhead from Actor, also my custom class does not need to exist in the game world. It is simply a wrapper for some data and helper methods. Instantiating and using objects of my custom class works fine.

However, it seems I cannot call any (Kismet) System Library functions from methods of this custom class. It would work if I derive from Actor, but as said, I don’t want all of Actor’s overhead.

Now, from which standard UE4 class should I derive my custom BP class, to get as less overhead as possible, but still being able to call System Libary BP nodes?