I always wanted to see some Fallout stuff in Europe. 
With Vaults, and FEV, and other stuff...mixed with post-nuclear Catholicism and national issues. Knights Templar instead of of BoS, anyone? Ghoul holocaust, anyone? German neo-Nazis, anyone? Post nuclear EU as new Enclave? Real new Roman Empire, not that Caesar Legion wannabes, anyone? Ancient ruins mixed with modern ruins, anyone? 

SO MUCH potential.