- lasts until the shooter's next initiative count, unless interrupted;
- provides a free attack on anyone in the affected area when it's declared;
- has heightened effects for weapons better-suited to suppression (thereby finally making machine guns worth using)
Some thoughts. First is that if this action covers more than the tiniest area, that makes it by far the best attack in the game. It's better than grenades, even, because there would be no damage drop off. Also, if this is to represent an entire round's worth of shooting, getting to make all your attacks at the beginning seems ... I dunnno, unfair? At least inappropriate. I'm ok with the action working that way, but I would instead move the attacks to the beginning of the character's next turn. Something along the lines of "... at the beginning of the character's next turn, he may make a final attack against any opponent that is still in the targeted area."
Second, I have in the past considered a "Volume of Fire" weapon quality, or some such. The idea is that it would allow guns with very large ammo capacities and high rates of fire to cover fire (or suppressive, whichever targets an area) a larger than normal area. My thinking was 5 bullets per square, like it is currently. So a typical assault rifle or LMG with a 50 or 100 round drum/belt could gain VOF(3), indicating a 3x3 area. Larger weapons, like HMGs could get VOF(5), and things like vulcan cannons and the like with 1000 round capacity could have VOF(7) or higher.