And this would mean many hard locks, Lots and lots (like 20) of Guards with a Captain, complex system and ofcourse GREAT cash, item and respect among the criminal community Prices.
Traps might be a little off (Have you ever seen a bank with spikes coming from floor?)
Also these big cashy places would mean that you might have to take a tour or steal blueprints or pribe a guard or an employee to get information.
These places should slowly re cash itself and they would hire new better guards to defend it.
Then there might be some middle rated places too: Just robbed banks second class rich people etc.
And the richest places would also mean that there will be many fellow thiefs also planning their own movements, alone or in teams.
So that would make a possibility to team up with an expiriensed thief to increase your possibility to rob the place.