There is no native to do stuff like that, but that doesnt mean that it is impossible.
For changing unit textures you can use that Toadcops dynamic texture changing thingy, which can be found from wc3c.net. ( Its called DUSC if I remember right )
For unit projectiles you should sue some projectile system, which handles all ranged attacks, instead of using normal wc3 ranged attacks. This is cool also because it allows you to make for example some slow time stuff that slows ranged attack projectiles. ( Like Blueshift in Tides of Blood )