Air support smoke grenade: this could be a cool feature for certain maps (like Iceland or Siberia) where once you reach level 15 on engineer you could unlock a air support smoke grenade that replaces the normal grenade and can be used to call in a strafe run with a animated fighter or bombing run with a high altitude bomber, you can adjust to see which one will come in and they will have different colors and reloading times (fighter is 3 minutes and bomber is 6
minutes) It will leave a red smoke spot where it was thrown and can be countered with anti air (it takes up to 20 seconds to come in depending on conditions)