Any kind of body position feedback would be amazing for new users.

At least put 3 lights in the training area, on a dummy or above my HUD health bar or wherever, that each light up on a green/yellow/red gradient every time I try to do a move. So if each body part is in absolutely perfect position, all three lights come up totally green. If my head is in suboptimal-but-acceptable position, the top light is yellower. If my left hand is rotated wrong, the bottom-left light is red. (Better yet, show the lights as little floating 3D body parts that follow my movement. And after I attempt a move, make all the colored body parts freeze in position against grey shadow-parts that show ideal positions. That way, I can look more carefully and see exactly what my form looks like)