My vote would be # 4. / and 5.

There are several other coins that have tried auctions and it just doesn't work.  I'm sure someone would buy a 486 processor for UTC, but it's hard to get good products listed.

   If doing a traditional store, as I mentioned;  you could easily import certain items, buy certain items on ebay and even have special items acquired during certain superstore sales.   Possibly you could conduct a survey of items people would wish to purchase, but most likely you would have to be able to maintain none to minimal stock.  There are many things out of china that can be bought in small lots; which have a decent mark-up in the states.
    A small example is the little cigarette lighter USB plug-ins.   You see these a lot in the States at gas stations and such for 4-5 dollars;  delivered from china these are about 1.40.  Solar panels, batteries, chargers, inverters and many other things can be purchased like this I suppose.  

   Many people on Ebay currently purchase items on sale at superstores like newegg.  These are sometimes 20-30% off normal price.   There are quite a few powersellers on ebay that, list these same items @ newegg price after the sale is over.  This would allow "special" items to be listed in a market;  camera, PC component, audio, etc.  

   You could have no stock and just drop ship items; however that would limit price, location and possibly delivery times.  As well, you would need to find 2-3 distributors willing to sell single quantities.  Worst case you'd have to buy lowest retail price, but again limits volume relative to pricing.

dunno, just thoughts