The plans for the Dulwich Picturehouse show what is a small cinema with three screens, two of which are very small. There would seem to be scope for a larger Picturehouse on the Capitol site and the upper floor foyer would make a great bar/cafe. However, I doubt that this would be probable especially as the Picturehouse group was sold to the Cineworld chain.
I understood that the upper floor foyer and its fixtures and fittings were protected, hence Wetherspoons was not able to utilise this space as a separate restaurant area.
If it were to become a (one-screen) cinema again, I'm not too sure it would be able to complete against the multi-screens.
Perhaps, Wetherspoons will be interested in taking the Windmill back over though..?!