@Gson - Up until the 5:30 mark, the guy doing the analysis is full of shit. You rotate on the lower half, not stretch some adductors in the groin area. "Keeping the knee back" is the antithesis of what you want to do. And this whole hip tilt from his leg lift is a big pile of do do. Your hips can't rotate until your hip line is parallel to the ground. All that excessive lift does is delay your rotation and create timing issues down the road.
Arm angle outside ninety will be a problem at some point if he doesn't do something about it. The block on his front side (plant leg into landing) is not good and needs improvement. He will gain some velo there.
The guy the analysist says he loves, Dominguez, his lower half mechanics are much much better than Espinos and would be a good model for Espino to look to.
Not sure that all this talk of development (as in adding strength) is going to serve Espino well. Velocity in pitching isn't directly correlated to strength. That is why no Olympic power lifters, or Mr. Olympus body builders throw baseballs. Velocity is more correlated to the stretch of the soft tissue and its ability to rebound from that stretching. That he clearly does very well. Probably the best thing a strength coach could do for Espino, is leave him the fuck alone.
He looks like a good young thrower, that will take some lumps going through the minors. He will have to make some adjustments to his mechanics as they don't lend themselves towards being a real high percentage strike thrower. But he has that equalizer - velocity - and that will carry him a long ways.