I don't think that real-time / turn based should be switched in the options. Games that allow you to switch that in the options always give me the impression, that the developers didn't know what they wanted, or wanted to please everyone.
If you consider switching between real-time and turn-based (e.g. for a single character / an easy fight), you should somehow integrate the switching into the game. I don't know how to do this, the switching should feel natural, not like clicking on a "switch plate". If I have an example or an idea to illustrate what I'm talking about, I'll post again.
