Requesting addition of a mechanic that allows a character tossing a hand grenade to Call Out the grenade to their allies, thus granting a bonus (or Advantage) to any Saves inflicted by that grenade. This is not a feat, but a baseline mechanic written into the basic hand grenade rules.
You shouldn't have to "unlock" the ability to communicate with your teammates well. It might be good to make the mechanic explicit as a trade between stealth and avoiding friendly fire.
Requesting addition of a mechanic that allows a character tossing a hand grenade to Call Out the grenade to their allies, thus granting a bonus (or Advantage) to any Saves inflicted by that grenade. This is not a feat, but a baseline mechanic written into the basic hand grenade rules.