I also tried to take the 2D version of some movies originally made in 3D and use the TVs own 2D to 3D conversion feature. While it obviously causes some artifacts and sometimes adds depth where it doesn't make sense (mainly TV screens inside the movie) I found that it worked surprisingly well.
Primarily, though, my wife and I use the 3D for the two player fulllscreen feature when playing games in split screen (Mario Kart 8). This is actually really cool, since it allows both players to only see their own part of the screen and also see their part in fullscreen.
Of course watching a romantic movie next to someone frantically playing a BF1 match probably wouldn't fly.
https://www.youtube.com/watch?v=bbRG-KfWyVc
And other 3D TVs could replicate the idea:
https://www.tweaking4all.com/video/gaming/split-screen-game-...
Both took advantage of the fact most 3D formats were just two images side by side, so if you took something that could put two separate streams side by side like this:
http://www.kvm-switches-online.com/splitmux-hd-2lc.html
You could do exactly what you described.
One problem I could see would be any cross-talk. Normally cross-talk makes things look blurry, any cross-talk would result in seeing fringes of something completely unrelated to what you're viewing. But with active glasses (or high quality passive displays) I don't think it'd be much of an issue.
That's exactly it! The "no more split screen" use case is also something I thought of but forgot about :-)
Whereas for most games, it didn't add anything and sometimes it was even annoying (for example in AC, the placement of the HUD was way too close), for Uncharted 3 it really added some depths (pun intended).
I've done 3D movie nights at my house with friends. Of course there's that one friend who comes (knowing it's a 3D movie night) and then says they can't watch 3D and insist we not do 3D...