The Demolish Completely button which cost 5gold/building is indeed one of the most useful features in game. But this Pay-to-Win feature can became unfair when someone else try to conquer the higher pops village of super-gold player, and then that village suddenly become full of crannies with small population left. This make conquering no fun at all.
Therefore, I'm suggesting a reasonable cooldown applied to this feature. And the more usage of this feature, the longer the cooldown will be.
I.e first usage 6hr cooldown, then additional usage within 24hr after previous usage will add +3hr cooldown and it's stackable with max 24hr cooldown. Stacked cooldown reset after 36hr. And if dev want to make it more fun n profits, then each stack double the gold cost too.
*normal ways of demolishing buildings is not affected.