Q.G. de Bakker , Sep 27, 2012; 03:35 a.m.
Heat, as you already mentioned. The camera lenses have shutters and diaphragms that need to work quickly and reliably. Who knows how they would stand up to excessive heat. I wouldn't like to try with my lenses.
The mount: how to fix a lens to a projector at the correct distance to the slide.
Nothing else, i guess.
You could try finding better projection lenses, even if that means switching to another projector. But that fish-eye trick will not work unless, of course, the same lens is used.