spy:
shield- it replaces the gun. the shield creates a visible forcefield around the spy that last as long as the cloak (maybe the shield and cloak can share the same energy bar). the shield has a 10 foot distance around the spy. as long as he has it on, he cant shoot out of it and no one can shoot in. if enemies come inside the shield then enemies can attack the spy and vice versa, but because of the radius of the shield, then enemies can still keep their distance from a spy backstab. if allies walk into the spy's shield, they are not protected by it like the spy is. if a spy wants to turn off the shield and cloak, the shield leaves behind a trail like a teleporter for a few seconds. this stops spys from invulning to an enemy base and then quickly disappearing. it is meant for defense from a distance, but if an enemy pyro gets in the spy shield, then the spy is pretty much done for. plus the shield is very visible to others.
the reason i was thinking of this shield idea is that it would help prevent spawn camping. a spy to immediatley shield and leave the base to disguise and backstab the spawn campers.