Lots of good stuff here. First off, depending on location, have him stock up on cigarettes and dip, that stuff tends to be a steady seller IMO.
Along the same line, Swishers/Al Capones/Primetimes/Pom Poms are all things that guys who don't know any better will pick up. If they realize they don't know anything, they'll turn to more traditional smokes. Therefore, Backwoods will fill the transitional niche nicely - they're a good smoke for someone starting out, and the way they look is attractive to the guy who knows little about cigars, but wants to look like he's smoking one.
From there, go a step up:
Quorum
David's Choice (excellent bundle cigar, though for the life of me, I don't know where you'd get them)
Arome de San Andreas
Mr B's
Any of the factory seconds, bundles, house brands that the bigger retailers sell.
From there, a few recognizable names. Things like RyJ, LGC, Montecristo are good, for two reasons
1. They may be names heard in the movies, and therefore are recognizable
2. They may be recognized as Cuban names, so the guys purchasing them will feel special.
A few premiums, Padron 1000/2000, CAO, Fuente, LFD etc - if the guys coming by like cigars, they may google it, come across a few big names, so a few on hand will be good.
In addition, I think that a hookah looks sharp in a shop. Customers may recognize it, and want to try it, ask questions about it. Weird stuff like this builds rapport, it'll help the store get regulars.
A line of accessories, a few Xikars for the guys who get into it, otherwise, some cheap plastic (those 7.00 ones work nicely) cutters.
A couple humidors, as well, have a catalogue of stuff that you can get online. Tell them that you would be happy to special order them a humidor.
That goes for many things, special orders from online retailers will ensure that this shop can get anything for its customers, without maintaining an expensive and excessive stock.
A couple events, maybe once a month, have a "free cigar with purchase" night or something, do some tobacco tasting, introduce them to pipes, give out cobs and a bowl of tobacco to get them interested in something else, have them bring their buddies, whatever.
(My local shop had a barn burning a week or so ago, I didn't attend, but it drew a crowd)
Best of luck to your friend, and I hope all the info helps.