it would be great if you created some melee move where you crouch and grab onto a knocked down opponent and punch him in the face a few times before he gets up.

that would be funny but would also be subject to spamming which would cause less people to play its also not very gentlemanly

continueing on the subject you could add a stomp or a prop up move i.e you knock em down and stand em back up to knock em down again.

or you could introduce more melee attacks kinda like martial artsy stuff but i think that would kinda over exert the current engine

more melee attacks

There's a topic on this already.