Would it be impossible to do NCL-BKK even weekly with a 777?
There are no airlines I could think of who would offer this.
What a shame that airlines like Eva Air operate into Heathrow. Their daily Taipei-Bangkok-Heathrow 77W flights could just as easily channel their UK-bound pax through a regional airport. It is operations like these that NCL could usefully go after if the runway is ever lengthened to cope. In the meantime, maybe MAN/BHX/EDI could step in and create a BKK link. Eva presumably only needs to top up at BKK as most pax will be LHR/TPE-bound.