I had a thought about how ruins could be more useful after being looted. Right now they provide a wall bonus, but that seems to conflict with the new towers...and the fact that ruins can't be razed makes them somewhat superior...which makes no sense.
Here a few ruins types that I came up with....
Fallen temple....basically a temple that is infested with undead. Once a hero destroys the foul denizens (and collects the loot), the temple is restored to its former glory and can provide blessings, etc. Yay!
Haunted tower....you probably get the idea..its a tower...undead...hero kills them...loot, and now you have a tower! Yay!
Cursed village/haunted mine....the village is under an 'orrible curse...the populace have been turned to frogs or pigs or statues or are in a magical slumber...a hero can break the curse by killing the undead fiends responsible..and the happy villagers/miners join the hero's cause out of gratitude....you get a village/mine/unnamed economic site! Yay!
Cursed city...not sure this is necessary, but see cursed village above and replace the word village with city. Yay!
Why do I think this is a good idea? Because a looted ruin doesn't just have to sit there looking sad anymore..it (and others like it) can now lead a productive life and serve the community. Yay!