Very nice POTW. The fixed powerstruggles are good, the multistruggles better. But I agree with Growler's drawover, all of that would look good and, aside from the light and dust coming out from behind Goku, wouldn't cut into FPS much if at all.
Giant mass of energy - One big sprite that hides the beamheads.
Explosive beam starts - Two crossed sprites like the beams have.
Thicker beams - Coding to enlarge beam sprites.
Motion blur - Already implemented.
Dust - Already implemented, just need to change the direction it flows in.