The only problem with that sort of idea, is that the more a shop gets stolen from, there's no way for the shop owner to defend their store from you thieves who get better and better. Now a roll, counter-roll system might be nice, but a store owner could theoretically ignore the roll and just keep on going with their business.
To be honest, its a workable idea in my mind, but you might as well just play ro-sham-bo for it or talk to the shop owner about trying to steal from them in order to rp it out. Whats the fun of stealing if you don't stand a chance of getting caught? Not to mention we do already have a dice system in place that could easily be put to use for this idea, but it would require you to talk with the shop owners before hand.
After all, this is a roleplay site. So while having mechanisms in place to prevent cheating, GMing, and the like is good, at the heart this idea in my opinion needs to be centered around playing it out. I like the idea of allowing people to trying to steal it, but rp it out. Flash programs be damned =P

