Whatever happens at WFD it is unlikely to take away much bizjet traffic from MAN. One of the major advantages of private jets is that you fly when YOU want to, often at short notice. MAN is H24, all-weather, has comprehensive facilities, and night noise restrictions don't gnerally prohibit today's bizjets. I can't see WFD ever being able to ofer all those advantages. Sheik al Makhtour, the Glazers, Roman Abramovic etc are not going to be impressed when they are told that they can't stay for that extra cocktail after the match because of the curfew at WFD, or they have to stay because the weather has closed the field.
Operationally, despite the 2000+ metres of runway, WFD will be somewhat limited for commercial flights by the large lump of Cumulus Peat-Bogostratus (aka Kinder Scout) which rises to over 2000 feet on the extended centreline.