How To Expand Event Graph Behavior (derive UEdGraphSchema_K2)

I want to enhance the Event Graph for one specific Actor Type to achieve some customization we need, e.g. pin colors for custom types, restrict available nodes for the blueprint, restrict node connections (execution pins) on the graph, etc.

It seems to me that for all these things the UEdGraphSchema_K2 is responsible. However, I found no way I can override/replace/… the Event-Graph Schema (UEdGraphSchema_K2) for this and I found absolutely no info on how to do that. I looked at the code but the FKismetEditorUtilities have everything hardcoded and there is no way to override that I want a derived schema to be used for the actor.

Does anybody have an idea how to do this? The only way I see it possible is to edit the engine code: The way it is setup i dont see how a plugin could even help with this.