OK, we are getting closer 
In the settings of the slideshow (F2), you can select “Start with current image”. That way, when I call “Slideshow - Play All” (F9), it will start playing with the selected image.
The only problem is, that by default, it will start playing the Slideshow automatically. So there is an option missing, something like to uncheck “Play on default.”
However, as you mentioned, you can either select a longer interval time by default. Or, you can press the “Space” key right after opening the slideshow. That will pause it.