Simply saying "be more capitalist" might work, but I'd say build more quality homes on all the scratchy pieces of land that exist round Berlin is an equally good option above firing people into the weird world of London property.
Finally the AirBnB/rentals thing is a result I'd guess of the massive number of people who hate having tourists traipsing through their buildings. My experience at least centrally was of large shared blocks of high quality flats and a lot of suspicion around strangers being granted entry to said gated communities.