Seems like once you start discussing what ifs or multiple possible scenarios, any straight answer or one-stop solve it goes out the window, best answer is simply you need to address what ever situation(s) present themselves with the tool kit you have, and hopefully that tool kit (both mental and physical) is sufficiently flexible.
Point in case - Drop bear, you said there would be issues if you went to do the head kick and how this could disadvantage you if the guy had mates present. I have no issue with grappling in itself but you go on to then suggest a sprawl or to grapple as a better option...let's think that through - if there were other assailants around I would absolutely not go to ground, you're signing your own death sentence, even if you're the greatest bjj guy out there, especially if there is a gun/weapon in play. Surely you see that? Perhaps more back to what you may be familiar with, if you do any bouncing, have you ever seen a bouncer go to ground in a club or on the street front where there are tanked up mates of an assailant/trouble maker present? I have never seen that, never, not ever.
If there is just the one guy, immobilise guy, recover gun...unless of course there is greater distance between guy and his gun and you happen to be the closer to the gun (in which case pick up gun and say "stick 'em up jack" (in which case if he was on all fours he would fall on his face, hehe, or shoot him in the knee/face, whatever is legal in your neck of the woods or you feel inclined to do), every scenario has its own responses.
Focusing on the weapon and not immediately negating the opponent, you forget the risk of the opponent having another weapon (do all of us only carry the one weapon, I mean, defence aid? - no! (another gun, bang bang or that knife he sticks into your thigh as you try to kick his gun away). Otherwise, you simply open yourself up to letting him take the fight to you on a more even H2H basis (to always be avoided, stacked decks always best).
If there are numerous assailants, then you need to get rid of (either by claiming or by kicking away, ie under a car, skip bin etc, such as ballen's example) the most immediately dangerous item to you. One bullet from the gun to your head from his mate while you are merrily neck-cranking and you are gone for good. A kick to your body or even strike to your head while you are kicking away the gun you have a better percentage from rolling with and continuing the fight. You then take the fight to the opponent that is the most immediate threat and then take it from there.
All the above is correct, and that's guaranteed.
....K-Man, K-Man, are you there, are you really "out of this thread"???!!?? : )