I agree. Interesting idea but no way would I want to sit in a seat at the Belasco for 3.5 hours (or any Broadway house, for that matter). I would hope they include an intermission but even that won't make it worth it to me.
I saw a screening of Aliens at Town Hall once. At 2 hours & 17 minutes that was a very bad idea. Besides the fact that the seats were uncomfortable, the screen itself was puny & inadequate. I can see them erecting something more state-of-the-art at the Belasco, but unless they replace all the chairs with recliners, I'm out. :P