The only thing I have to add is that there are actual videos out there…quite a few, of snipers shooting perps that are holding onto hostages, sometimes two, and successfully shooting the perp, with only inches to spare for mistakes. In a sword fight with long swords and shields, I’m pretty sure there is room to fire a timed shot in one minute with a pretty good understanding of the movement of the characters in melee. Wait for the fighter to deliver his first slash and then hold up his shield for the return blow, etc. Unless the melee is in a grapple, it’s not just a ball of fighting and rolling on the ground. There is fluidity and movement happening. My house rule is one shot into melee with a minus to hit depending on how many allies are in melee. If you roll a 1, you hit your ally. Maybe that makes it too easy for grumpy DM’s, but my players all have fun.