I don't think it would defeat the purpose. It would instead allow transitions where there didn't need to be a frame that covers the whole screen. Instead, you would have an animation that still always shows things underneath it, but part of the animation swipes across the screen in a way that would support a swipe transition underneath.
That said, I don't know how easy this is to accomplish.
If you don't cut on the cover frame, then it's not a stinger transition by definition. It's just a video playing on top of stuff.
Now as to fading between scenes with a stinger on top, that would require what's commonly referred to as an MLE (Multi-Level-Effects) architecture... which could be added to OBS, but man, the interface (unless OBS starts to look like a real-life switcher) would be a royal pain to deal with.
I mean, in the end, isn't a stinger transition also just a video playing on top of stuff?
And it doesn't need to be anything complicated in OBS. The option window can be as it is now, all that would have to be added is a drop down for underlying transition effect (cut, swipe, fade) and add a duration setting for applicable ones (swipe, fade) and a direction setting for swipe.
No. A transition gets you from point A to B, in this case Scene 1 to Scene 2. If you don't do that, then it isn't a transition. Period.
A Stinger is a transition that has at least 1 frame of complete coverage to move from Scene 1 to Scene 2 without the viewer seeing that cut. If it doesn't have that, then it's not a Stinger. Period.
So you're saying that each scene would ALWAYS get those 2 transitions that run at the same time? Hmm... that would be one way to do it, but I see that as rather confusing for newbies. Also having such would be a bit weird interface-wise.
Also again, if you're fading from one scene to another and try to put a stinger on top, if you're not completely in the new scene by the time the coverage frame ends in the stinger then the stinger is no longer a stinger. It's just a an event-triggered DSK animation...which is why we need proper DSKs and a macro/linked-trigger system, so you can do what you want.