The Wild Man (Tom) has probably done it. That dude is hardcore, and has some hilarious stories involving riding. Stick around a bit, and you'll probably hear a story that involves the partial consumption of a dune, I swear it.
Relocation sucks in the moment, but I think in the long run they'll be happier down here. I stipulate that they further deserve a good severe beating in addition to being fired from "public service".
On the thicker barrels it doesn't really matter so much, but there are some experts who feel that an overtorqued set-screw type can affect accuracy... That's FWIW and YMMV...
I think all the suggestions so far are great. I would suggest that standalone systems would also sell well, like a gas system, BCG as a whole, LPKs, and such-like. Things that can by themselves bring a whole build together.
Adjustable GB can keep you from experiencing overgassing at the user end. May not be a problem at all, but you might stumble upon a particular load that sends lots of nice smelly gas out of your ejection port on every shot.....
Ya know it's really strange, the demand for electricity just never goes away.... <dontknow>
Actually, I've been on strictly 40 hour weeks since the beginning of May...
Follow the links for more info:
http://www.ncwildlife.org/News/NewsArticle/tabid/416/IndexID/9208/Default.aspx
http://www.newsobserver.com/2013/08/02/3070508/gun-suppressors-are-now-legal.html