If OPC could be scripted to use and sign prepared contracts (which I don't think they can atm) then the flexibility that would afford would definitely allow an OPC banker, which would be exceedingly cool. If that were the case, one might create multiple characters with the bank tellers being automated in their specific tasks, in this way one character could almost run the entire bank presuming he bought enough sparks and was an excellent scripter.

With the exception of having hire a few guards and transporters, maybe another manager here and there.

Would be really cool in my option to see cleanly run organisations like this.

While the idea is definitely cool (reminds me of the old SWG macro scripting) I believe the OPC scripting will be modular. So instead of you writing out the script yourself (or copy and pasting it) you simply drag and drop pre-made script modules that the devs wrote. I think this was to prevent players from scripting their OPCs so they can be used in the ways you described.

The original idea for OPCs was for an AI to take over your character for you while you are offline, effectively turning him into an NPC. They would then take the scripted modules you give them, which are basic commands, and then fill in the blanks as the OPC goes about doing a series of simple tasks.

For instance, You are a farmer, but in the middle of harvesting your fields, you have to go offline. So you program your OPC to finish harvesting the available crops, store them, then return home to eat, drink, and take care of itself so it is alive and healthy when you return. It is basically a caretaker for your character.

But, from what I understand, the OPC will also react to things happening around it. For instance, if someone tries to break into your home, you can program the OPC to try and fight them off, or to run for a guard.

So you can make a complex OPC, but not in the way you are hoping. You can only really program it to handle specific situations on a minor level.