Combining with other filters requires initial "off" state

If I would like to use both other filters like Texy, and this as the default/main WYSIWYG feature, then there is a need to be able to let the administrator decide on its initial state being on or off, and preferably also a way for the administrator to both set its default state and also give certain roles the option to overrule it in their account page.

Initially, I would like the editor to be off, so that it does not affect existing hand-coding or the like. Users can then continue dealing with such posts in the way they please, without being forced to use this editor where it does not fit, or before they have time to adjust the existing codes.

So I suggest that under the body text area, or perhaps right above it, there should be a toggle link that turns WYSIWYG on/off, which adheres to a) the user preferenced state, and b) the default state if no user preference has been set.