Quick idea… I think this would help incite raids…
1- when a raid is successful, the raiding player should be able to steal more than food and iron. For example, some if not all crafted but ungathered battle items / trained heroes / recruits
2- hinder construction progress / deteriorate existing buildings (introduce a concept to repair buildings where for example a raiding party decided to downgrade buildings rather than steal ressources or battle items
Cheers from Montréal !