I've seen one design which seemed to address a similar problem well. It was a small theater of 5 seats, 3 in front row and 2 in rear on riser. A big "gap" was left betwen the 2 seats on the riser directly under where the projector hung, and a nice shared end table was installed between the two rear chairs. So, essentially nobody sat under the projector.
Since the gap size was arbitrary, it was chosen such that the second row seats were staggered off of the first row. This lets you get buy with a much shorter riser.
To top it off, since the two second row visitors would have their ears fairly close to the projector, it was mounted in a hush box.
Finally, are you going through the building permit process? Our local guys wouldn't give one for something like this, the ceiling is too low for habitable living space. They would force you to classify the area as C.4 Storage, and while they would let you build it, you would never be able to count the space in your total habitable square footage if/when you go to resell the house. That bothers some people, not others. I wouldn't let it bother me, but I wanted to point it out.
Rhino