Ask in the map forum. I don't think its possible to change the unit's projectile without replacing another version of the unit which has the different projectile.
Pick an archmage, make him pick a fire orb. His missile is no more a frost mssle, but a fire mssle. why is that? go check it out in Object editor, and go check the fire orb. when he will pick up the fire orb, he will have your mssle. but if you want a melee to transform into a range you gotta change the units. was i clear?
LIES you can use a trigger but im not sure witch my friend made a map that changes melee to range. Just look over every trigger in the editor only takes an hour.
