Binding Objects to List for ArcGIS Python Script Tool Parameter?

Since you know that you can provide a potential list of acceptable values to a tool parameter, you could try using the selected value from the domain, as the key to a dictionary residing in your main script.

Have your dictionary object contain a key of the same name in your drop down list.

If you're feeling adventurous, try creating a class with the default property __name__ set to the value you want to display in your drop down list. Though this is getting over complicated and not very pythonic, it might correctly bind to the drop down list and assess this default property and deliver you the functionality you want.

I say might. I have not tested this and am skewing programming idioms (I'm usually a .Net developer).