Engines for VTOL flight

I'm interested in building VTOL aircraft, so one thing I think is missing are jet engines which can be swiveled 90 degrees like in the Yak-38 or the F-35.
The engines in the center of mass of the aircraft are also important and for example, the F-35 uses ducted turbines linked to the jet engine. Ducted fans with tens of blades in general are common in quadcopters and other UAVs.
Finally I have to mention the weird engine used by the Harrier jumpjet. I feel that's a bit of a dead-end technology and not so interesting, but some people might feel differently.