3. Does NCL have potential to host a second Middle-Eastern airliner to a destination in that area, such an airline to Abu Dhabi or Doha?
No.
In terms of Iceland, I've just finished working as a Christmas temp. at HMV in Newcastle City Centre and I didn't serve a single Icelandic person but I did serve a big amount of people from Germany, Denmark and the Netherlands.
Re-read the post: ".....Could see it working with FI,
provided it linked conveniently with KEF flights to North America.....", and ".....
and not if it "dilutes" GLA....." FI have a route to/from GLA.
It's probably the nearest that NCL will ever get to a North American link, as there are already direct flights to/from there are to EDI, GLA and MAN.
BTW, the entire population of Iceland is less than that of Croydon, so it's entirely possible you wouldn't see any in HMV-Newcastle, even if one or two turned up in Newcastle.