hi

you might also consider making a lens from cells purchased at a place like the surplus shed
single cells have a very large image circle ... you wouldn't need to have a pinhole lens, and still
use paper negatives with exposures of a few seconds rather than minutes. you could cut light down
by making your own fstops &c ...
for the paper, i would make yourself a roll back.
2 large dowels, with the paper running between them.
when you make an exposure, you just roll it to the take up spool and make another one.

you could make a dark-slide as well, so you could remove the back from the camera ...

sounds like a fun project !
john