See no case for Jet2 to operate 2 varients of the 737. The 737-800 has 189 seats which is only about 5 more than the A320 these days. With airlines in direct competition with Jet2 like easyjet phasing out the A319, Ryanair and TUI operating the 738 and larger MAX models Jet2 would just be handicapping theirself with a smaller model that has considerably less seats.