Allow individual nodes to be disabled and permit upstream inputs to be passed through if possible, else disable downstream nodes as well. One way this could potentially work at a high level is to check if the "primary" input type (e.g. an image being modified) matches the output type, then the input is just passed to the next node. If the "primary" input type does not match the output type, or there is some other factor that would prevent a sensible input/output connection, then all downstream nodes are disabled as well.