Way to increase blast damage resistance?

I wanted to create a Swiss civ inspired by this video

I’d like to increase blast damage resistance for units (as seen for the first UT in the video) but i have absolutely no idea on how to make it. Slavs, Poles, Britons, Byzantines and ofc siege units can make blast damage. There’s a “Blast damage defense” attribute in AGE but i don’t think that it works in this way.

I’ve seen there might be a way to create it in the scenario editor, is it possible on AGE? Any idea?