You probably just hit a couple of nails squarely on the head. I work with very high pressure fuel pumps that look stikingly similar to this concept. Most of the working internals are superfinished tool steels or ceramic. Big bucks.
As RPM increases, the demands on the injectors, valvetrain and ignition system will increase at 3X the rate of a standard engine. Keeping everything moving, timed and controlled at high RPM is probably going top be difficult (read: expensive).
a few years ago i saw a prototype F-1 engine with a notched cylinder running along the top of the head that acted in place of the valve train with the notches opening and closing over the input and exhaust ports. it was crank powered turning over ten grand too before running into problems. i wonder how it would work on an engine like this that doesn't turn high revs???