Cuban,
" However, jet engine nozzles have to be rather short by nature of what they do. It is a total non-starter to have lengthy ducts from an engine core to its nozzle - someone try and think of an example anywhere, there aren't any! "
I immediately thought back to my own jet training and that of thousands of other RAF pilots from a few years back. I think we'd all disagree with that.
Take a look at the Jet Provost series of aircraft. That aircraft was developed from the Piston Provost, which of course had the engine on the front. They put a turbo-jet just behind the pilots and led the noise down inside the fuselage and out the back end through a long jet pipe. Seemed to work alright for about 40 years and up to about 400 kts for the Mk5....
p.s. There was also the Hunter - that type held the world speed record in the early 1950s and went on to be a well respected fighter and trainer for a similar length of time as the JP.