Reference to a certain class / script

Hi,

I want to have an trait object where I can define:
- Type of order I can give
- Towards what kind of objects this order can be given

My aim is to define "this unit can Attack buildings ( objects with building component)" style combinations.

How could I approach this?

I thought it would be nice to have variable in inspector where I could just drag scripts in and define types that way, but that doesn't seem possible.