Central engines
Well, the central engines are fascinating, and unfortunately there are limited numbers of new trijets in production - not sure how the Tu-154 and Yak-42 lines are doing, the only brand new trijet is Dassault 7X.
I think that Tristar was also limited by the fuselage and landing gear design - there was a massive keel beam which prevented adding a central landing gear and increasing take-off weight or something.
But otherwise, Tristar and DC-10 were pretty close... why couldīt Tristar just use similar engines as DC-10?
And as for quick and dirty... wonder why then MD-11 got just pinched waist instead of a whole S-duct?