You've made a compelling argument for Diomande. Would afcon commitments be enough to put us off? Think if he could have a settle in season this year would make all the difference.
One thing I haven't seen mentioned is the fact that Guehi and Gordon are good mates. Do Newcastle think signing Guehi gives them a better chance of tying down Gordon to a new contract, and so are willing to pay an extra premium to get him as opposed to one of the cheaper alternatives?