Maybe make an empty scene, set the Scene Switcher go to that scene when the video ends, and while the video is playing take a few seconds to add any other scene you want to that empty scene.
I'm not sure I follow that. You're saying to re-build a potentially complex scene while a potentially short video is playing? Surely not.
Or is that empty scene just a "trampoline" of sorts, that stays empty, and it triggers another scene change immediately? Then you go into the settings and change the absolute target of that trampoline while the video is playing...?