The hardcore stuff sells very well for a number of reasons, but I figure that one of the big ones is because of something film theorists refer to as "THE SPECTACLE", otherwise known as "eye candy."
The hardcore stuff relies on brief, intense and extraordinarily visible interaction and reaction; there's no missing what goes on.
Lighthearted stuff is excellent, but as we all know from personal experience, the lighthearted stuff is composed of small, subtle, almost telepathically transferred moments; it's the FEELING, CHEMISTRY, and NON-VERBAL stuff that makes it a lighthearted moment, and that is a subjective experience, and THAT does NOT translate very well to a visual medium.
To convey light moments and their power, you have to DESIGN the images and then show them in a carefully arranged way, but most importantly, you have to rely on non-visual aggregates that work subconsciously:
1. Audible breathing
2. Creasing of fabric or bedsprings
3. The sound of moisture when a 'lee opens/closes their mouths
4. Room tone - taking all the ambient sound out of the clip since we block it out during a session anyway
5. Macro shots of clothing/skin/tackle textures, which require lots of intricate lighting
6. Expert knowledge of editing and sound design to manage this all effectively.
So basically, you have to artificially create the intimacy that the viewer is automatically left out of, and if you do that, any authenticity of the scene is GONE...try to maintain the sub-space when you're stopping to change the lights every few minutes. It's also more hard work than the point-and-shoot method currently employed.
The best source we can currently use is writing because the amount of information HELPS, not hurts; you can also go into multiple character's heads and report their feelings without throwing off the perspective.
But so far, any examples of people trying to do this visually are the kind of femme glamour-porn of Veronica Heart, Candida Royale and Michael Ninn...lots of stylization, but there's no tension or animal magnetism that makes sex or tickling so great. In fact, those are the videos we all laugh at for how fake they look.
I think it can be done, and am in the process of drafting some of these new prototypes at my drawing board...but I still don't think it can be done without ruining the authenticity of the scene.