yeah a shop would be a regulation nightmare at this stage, until fincen or whoever decides what they want to do with bitcoin i guess a shop is not v practical.
Even if you have an online xchange that only takes cash, 1. where would people come to deposit cash ? like u meet them in the street and stuff ? , 2. Even if you have like a shop or office, end of the day the cash will go to your bank account (unless u put it under your pillow but that doesn't make sense) lot of cash inflow to your account will raise alarms and then before you know it swat is raiding your home trashing everything
the people who ran the exchange would work out of an office. that office would have a front desk with a cashier.
no bank account. just a very large very secure safe with cash in it. perhaps you could buy up a building that used to be a bank.
If there was an earthquake then a fire, they can embed a message in a transaction to themselves on the blockchain: “Building Destroyed, Vault Intact, Credit Unaffected.”