For now, the 737 300's and 757's would do well out of GIB, so short/medium term there shouldn't be any problems.
Their new 737 800's have the Boeing Short Field Package included. "Basic" 737 800's and 737 900ER's (which have the SFP as standard) operate into shorter and less developed runways worldwide. Look at European operators into the Greek islands, as well as Indonesian and Brasilian operators, to name a few.
Payload restrictions might be necessary on some days, but I wouldn't have thought it would be too much of a problem to overcome.
Who knows, Jet2 might order some MAX8's, cseries or Airbii... Or maybe they'll try and get the A330's into GIB?