Except there are certain "bounderys" to which even modding can not do. We must leave that part to the hackers
List of what you CAN do:
-change unit graphics, attack graphics
-change button display
-unit attack, hp, sheild, and other properties
-add attacks, (Missile Turret that attacks ground) delete attack ^.^
-change unit names
but I think I am still missing some, wanna add anyone?