It seems like the hard part is the delivery mechanism to get the chemistry and the paper together in the field. You could essentially build a darkroom into the camera, which gives you something like the "Afghan box camera" concept, but if you wanted to use a "Polaroid-like" exposure as a preview for some other camera, that doesn't really solve your problem.
The alternative is to try to integrate the processing into a specially designed film holder, or into the film itself a la Polaroid/Fuji/Impossible. Both are clearly possible, but it would take a lot of work to get something really functional.
At one point there was a slight trend in "Pintoid processor" pinhole cameras made from Altoids tins, with rubber tubing built in so you could get chemicals in and out and process in the tin. The tins are sized just right for a 2 1/4 x 3 1/4 sheet, which of course could be film or paper; if you could find an appropriate larger container that would hold the chemicals in, the concept would be adaptable.
-NT