No timeline editor. But I add it as feature request.
Great this would be a great feature.
Why would he/she have to turn?
When having to stop the tour to show an image they would have to click pause and then show a pic.
Does your client want to the scenes to change strictly according to a preset time interval or also want manual override?
Also Manual Overide
Is it intended to use autorotation?
Did you consider the Previous/Next Strips plugin - see screenshot.
If your presenter was to use a touchscreen device, a tablet PC mounted on a lectern for example, to drive his/her data projector, then it would be very easy to move forwards and backwards through the scenes, changing scenes whenever it suited his/her delivery, and there would be no need to turn around away from the audience.
You could also have a control bar which starts closed to provide full manual override controls if required.