I just don't see Finningley taking much of a toll on either Jet2 or LBA as a whole.
It's so difficult to get to LBA from anywhere North of Leeds that those who would be tempted to fly from Finningley are the ones that already use the M62 to fly from Speke or Ringway and any foreigners wishing to travel to Yorkshire are unlikely to want to fly to an airport which sounds like it's in Nottinghamshire!!
It would be a nice easy divert though when the shroud of fog decends around LBA.
I do think Finningley has a role as a longhaul competitor to both Newcastle and Ringway, it just has to attract some big names. Virgin would be nice or an American carrier.
It would also be a good base for any prospective longhaul low cost carriers that may wish to start up, good deals on airport charges and handling will probably be available.
Maybe even a couple of freighter that are tired of the congestion at other northern hubs.