Tel Aviv and Gambia will not be on the scope of Jet2/Jet2holidays. Tel Aviv is catered for out of MAN by easy and soon to be El Al (or is it their LCC arm). I can only see BJL been added to the network as a charter for them on behalf of The Gambia Experience tour operator. Thus the risk is smaller - the aircraft and the staff are the only ones there. Once the customers are in Banjul/Gambia it is the responsibility of the tour operator.
They do not need the range anymore - the NYC market will be taken care of by the A330 which will move 327 in one go to EWR (and id probably guess eventually will be out of LBA in 2021/2022 with some figure bashing in HQ to make it work). That is why the Max 9, 900ER or A321 are good products for the airline to purchase for people moving.
If Jet2 were to order WB aircraft - imo they would be supported by Jet2holidays venturing into the long haul market. I personally think however there are a few things left to do in Europe first:
Firm up the Italian Network (Currently only serve VCE, VRN, PSA, FCO & NAP). Can see Sicily been added and maybe one more on the mainland.
Continue on the growth of the Greek Network - they have overtook TCX in what was once their strong market with Manos.
Success of STN/BHX will keep them busy - add another base in the Southwest to have full coverage of the UK.
Turkey. They love Turkey - so much so an A330 is going to DLM and AYT this year from MAN. Daily flights from STN, 7 from MAN, 6 from BHX.
Bulgaria - build up the volume into there.
Cities - continue to build these up. There is one or two maybe 3 they could go to - LIS/OPO, MXP/BGY, ATH, MAD.
There is probably a lot also going on behind the scenes within the business. I think Jet2/Jet2holidays are busy at the moment and as a business, you can never venture off into everything all at once.