Anyways, the floors in most theaters are icky enough. I don't think a TV screen would compromise the experience. At least you can keep up with the plot. Plus the glass is positioned in such a way that normally movie viewers are not facing it, as it is facing the screen with them. I still prefer this to the monitors in the stalls.
Speakers pipe the sound, and it is soundproof to eliminate that intrusion.
The design of theatres has gone down quite a bit up until recently, and I think stall monitors would not help. A one-way window would be excellent, but I agree that there would still be lighting issues. To address egnor's concerns about cost, the design of thumbwax's theatre could be looked at, and maybe rather than a restroom for each theatre, two theatres could share a restroom, with views of both screens. Sound problems would still need to be worked out, but sound can be directed at least to some extent. There might be some overlap, but again, we don't want people watching the whole movie from the restroom, so maybe that's ok.