ATM withdrawls are already two-factor - unless your ATM experience is very different to mine.
You need the card (something you have, factor 1) and the PIN number (something you know, factor 2).
You need the card (something you have, factor 1) and the PIN number (something you know, factor 2).
The only things I can think of that uses one-time passcodes are the occasional password reset or login from a new device? Are there other uses I'm not aware of?
Some people I know are still not comfortable using an ATM, if you add passcodes they are going to have a very bad time.
however, if your system allows one to disable even the PIN code that's pointless.