WI Developmental problems delayed perfection of the Halford H 1. jet engine so long that the prototype deHavilland Vampire made its first flight - in 1943 - with a piston engine?
WI Vampire followed a similar developmental curve to Saab 21 prop .... later jet fighter?
Yes, the thrust line would have to be raised to avoid nicking the runway. Alternately, longer landing gear would be needed.
OTL Yes, we know that Halford based his engine on developmental work done by Frank Whittle and that DH later bought out Halford and re-named the production engine Goblin.