“Very complicated and costly endeavour”. Make them do it. They need to be taught that “ooh, it seems to have caught fire after some dirt heaps appear to have fallen onto the access road” and “oh dear, the contractor got confused and knocked the whole thing down instead of just the unsafe bit”, are not acceptable practices. They’ll have to spend a large amount of time and money and will end up with still have a building on their land that they don’t want there. Do it.