Have read this board for awhile but first time posting.
I've often wondered the same thing about long snappers. I snapped in college and played DE. My typical snap time for a punt was .65 to .68 seconds. A good NFL long snap is anywhere in between .6 and .7 seconds. I know there are a ton of guys playing various positions in the NFL (usually DE or TE) that were long snappers in college. I've got to think at least a few of those guys have the capability to get it back there as good as most snappers (and you do see a poor snap almost every game, but usually the punter still gets it off). And just to your point about headhunting, the coaches could care less about the LS making tackles. Yeah they run down and try to cover, but they're usually not near the NFL caliber athletes as every other player on that punt team. Occasionally they make tackles, but I've seen Garrison Sanborn have his ankles broken more than a handful of times in the open field with a punt returner. All NFL teams care about from the LS is that the snap is fast and accurate.
I wonder if coaches are just too nervous of the storm that would hit if they had a regular player as a snapper and he did botch one. With today's mass media coverage of the NFL, you know people would be very quick to call them out for doing something different than every other team in the league.