The best way I think ground melee would work after thinking about it, is in order to go into flight mode, you would have to use the flight key ( f ). I mentioned earlier that we could also use the space bar, but I think I want to take that back .
Now, if the jump button has nothing to do with flight mode, that can leave possiblities for flips and acrobatics. Like if your running really fast on the ground, hit the jump key, soar the air and land back on the ground, its like you never actually left ground based fighting. Dashing can only be done on the ground, because if players could flip through the air + dashing, it would be hard to hit him. So doing acrobatics lets you evade hits and energy beams, but slows you down a bit.
Dashing on the ground could let you run I would say pretty close to swoop speeds, but is much more ki/stamina efficient. Downside is your on the ground, and an easier target.
SSj Goku, for your idea, the hop you mentioned (double tap) would happen, when your standing still, letting you make quick evasive movements, and if you continue to hold down the movement key, you break out into a sprint.
I was reading your first post, and instead of double-tapping the *backwards* key to do backflips, double-tapping it would let you dash backwards. Lets change it to the "+duck" key for the backflipping (or anything else) to give it some use.
Im assuming all my ideas would work under basic melee =), so it will be much more interesting instead of the usual swooping in the air + holding right click, which is all esf is pretty much based on right now.