No numbers i have seen stack up for the diesel unless you are doing huge hours, and that is without recent problems. Seems to me that there are some very practical issues with this configuration, e.g. decreased range and payload, lack of Jet A1 at the type of fields you are likely to fly to and the maintenance points already mentioned. Diesel had its attractions because of cheaper Jet A1 and uncertainty over the future of Avgas. The first has gone because of the duty hike in Europe on diesel for private flying; the latter is questionable as the demise of avgas has been predicted for years yet it is still around. If you believe that a long term replacement for avgas will eventually appear then what is the case for diesel?