If I may add a few thoughts of my own, as a veteran of both game stores and bars:
> Non-alcoholic is almost certainly the way to start. Illinois liquor laws are an absolute nightmare, and the business insurance for bars is likewise insane. You might be able to swing a "BYOB" license without drastically increasing your overhead, but...
> If there is alcohol, you will have problems with customers. You may be picturing a bunch of good-natured gamers having a couple of adult beverages as they play, and that's true for most cases, but you will have the occasional person who imbibes too much. Be prepared to handle belligerence or sickness. In other words, hire bouncers. They can clean and stock when there's not any problems, they can check IDs to save time at the counter, but mostly they're your eyes on the ground.
> Don't collect up a bunch of rare games and put them out for play. Pieces (and entire games) will get lost or stolen. Keep extra copies on-hand for spare parts, or concentrate on games that use generic pieces. You can get "meeples" wholesale for pennies each. If you're looking into BattleTech, track down a few copies of older editions with the cardboard stand-ups.
> Similarly, if you do decide to have nice miniatures on display, make sure the cases are locked. Gamers can be just awful.
> Get a good photocopier (preferably one that can also act as a printer) and keep it in good condition, with plenty of paper. Make sure your staff know how to operate, refill, and do basic repairs (clear paper jams, mostly) on it. Don't be stingy, either: it's overhead. Just make sure customers know that printing a few record sheets for a game is fine, but it's not there to print entire books.
> Don't just advertise to the "norms." Reach out to different gaming communities and invite them in. You're already doing this with the BattleTech folks. Do the same with those who play Pathfinder, the FFG games, Steve Jackson Games, TSR/Hasbro, etc. Most of these companies have demo teams and game finders, so invite them in. Hook up the agents while they're working; after all, if they're happy and relaxed, they're going to be better with your customers, which is good for both of you.
> Don't try to be a full game store, but do offer minor items for sale. I highly recommend stocking dice, at least basic Chessex bundles, and superglue. Pencils can be sold or given away as advertisement (and for the love of Cat, provide pencil sharpeners - something a lot of places forget).
Most of all:
> Do NOT suffer bad customers. This is endemic in the hobby shop industry. You want a wide variety of people in your business, and to do so you want to present the hobby as viable for the mainstream. The most common, specific complaint about hobby shops from the mainstream is that someone in the store made them uncomfortable. Much as we hate to admit it, we all know who they're talking about. Sometimes it's even a friend of ours. Don't let them scuttle your business. If they're a friend, make clear that you're running a business and that it's not somewhere they can hang out all day. If they're not a friend, get them out the door. You want to stand above the "average" gamer joint. One place I worked at even had staff meetings where we'd discuss regular customers, going so far as to review security camera footage to see if they were bothering "walk-in" customers.
These are just my thoughts from an employee level, so feel free to take or leave them (except the bad customer bit, seriously, you don't want those guys around). I'm in Chicago, so I'd really like to see you guys succeed. Best of luck!