A very simple suggestion, basically a grenade that creates a large smoke screen that lasts 2 turns.
Hedgehogs inside the smoke screen are either visible or invisible (not visible means you can't see the hedgehog or his crosshair; and his name, team color, team name, health etc. should be placed in the center of the smoke screen instead of directly above the hedgehog. If there is more than one hedgehog in the smoke, than there is a list of names, teams, etc. in the center of the smoke):
Friendly Smoke Screen, Enemy Hog: Invisible to all players
Enemy Smoke Screen, Enemy Hog: Visible only to enemy player and his allies
Friendly Smoke Screen, Friendly Hog: Visible only to you and your allies
Enemy Smoke Screen, Friendly Hog: Invisible to all players.
Perhaps it is also possible to make it so that if it's a friendly smoke screen, inside which there is both an enemy and friendly hog, then if your hog is close enough to the enemy hog, you can see him, but he can't see you.
Tell me what you think!