Overriding doctest directive

[TiemenSch]

Would it be possible for this extension to have a mode where it overrides the "selectable text" in .. doctest:: directives?

Having the >>> unselectable is by far my favorite addition of this extension, but otherwise I would like to stick to the more default doctest blocks.

[sbrunner]

Actually not but, I don't use that, then a proposition is welcome :-)