Obviously it's your group and you do what works for said group, but allowing a free attack on a Triumph feels a little too good, and could lead to problems down the road as your PCs starting rolling more proficiency dice on their Initiative checks, and could lead to instances of each of the PCs getting a free shot at the bad guys before the encounter really starts.
I'm not saying their aren't circumstances where it could be justified, but I'd want to keep those circumstances fairly limited.
The I think a single free action is not out of order. If the players have guns drawn and ready no reason they wouldn`t be able to get a knee jerk reaction to fire their weapon. If they didn`t have weapons out though and they don`t have quick draw they would have to use the action as a maneuver instead to get to cover or pull a weapon. Makes taking the quick draw and quick shot talents much more valuable in combonation with ranks in cool. You might get to use the talent twice if you roll a triumph.
I see it narratively like this. Players walking through the forrest of endor when storm troopers in ambush jump out, smuggler rolls a triumph and get a quick blast off as the first storm trooper moves from cover. He doesn`t have much knowlege of whats happening he just pulled and shot out of pure reaction speed.
Plus it puts a whole new spin on the 'Han shot first' scenarios.