Not really a mechanic in itself, but I would like to see a game from one of the big studios moving from the overused high school/married couple settings to the fantasy genre. Yes, I'm aware that there excellent NTR works taking place in high fantasy scenarios, but for some reason almost all of them seem to come from dojin studios (Makura Soft, NTRPG, Expiacion and so on).
Fantasy and therefore the inclusion of magic open a lot of possibilites for scenarios that would be too forced on the real world, like we saw in the great "The curse of Kubel". Unfortunately I don't see it happening soon: ANIM has always focused on present world scenarios, Atelier Sakura does the same (plus I couldn't care less about them at this point) so I guess that the only options remaining are either Alice Soft or Waffle.
I'm putting my faith on Waffle: they have been releasing NTR games for quite a while now, plus also recently focusing on the dark fantasy setting with the Eden's Ritter's series...so hopefully they'll be able to connect the dots and create a mix of the two at some point in the future.