At the moment at least in Germany you have ISPs advertising bandwidths and even selling contracts with bandwidth that can never be reached not because they don't have the capacity but because it's not possible to reach them given the technology in the ground.

We're currently in place that is completely unacceptable towards customers. Now you don't have to go completely in the other direction but when you advertise and sell someone a contract involving a certain amount of bandwidth, you should have to provide that 99% of the time modulo schedule downtime. I think that would be perfectly achievable and fair to ISPs and it wouldn't require them to provision for maximal capacity either. I mean it's not like you should be able to sue them into the ground when they only manage 89.9999% or something.