My 2 cents
In passthrough viewer pretty much needs to mimic what's happening on screen, so it's important that positions are natural and comfortable. As much as i love variety in regular vr, I'm not likely to stand in place or plank for 20 minutes.
A feature I'd like to see is an improved color correction, - having lighting color and levels close to what's happening IRL adds a lot to immersion. I don't have studio lights at home, and that unfortunately creates a separation. It might sound weird but i found some poorly lit videos to be more immersive in passthrough
Improvements to "fake 6dof" are needed, at it's core it's really cool, but too clunky to use. You need redo the set up with every single video, and readjust tracking every couple of minutes.
For stories, i think you can really shine with many "at home" scenarios. Gfe, cheating, hookups, escorts, 4th wall breaking talking directly to the viewer etc.