Field for c# Script for the Inspector / Drag and drop external scripts

I'm about to build a basic input/event -> output system.
This system should accept scripts from other users that derivative from an "Action" class and override the method "perform()". Those scripts just get added via the inspector.

Here is the problem. The inspector only allows "Object" class scripts to be dragged in, what kills the derivation and can't access the "perform()" method.

If i define the field to be an "Action" class object it does not allow any object to be dragged in.
If i make the script and field a standard Monbehavior it also does not allow the script to be dragged in.

Thanks in advance.

 

Code (CSharp):

1.     public MonoBehaviour behaviour; // drag any script that inherits a MonoBehaviour in the editor
2.  
3.     public void Perform()
4.     {
5.         behaviour.enabled = true;//Start your script
6.     }