I may have missed the point of the original post.

If you want to convert a Pentax 110 SLR to 16mm that would really be a fantastic project! From my own experiences building and modifying cameras, I'd say it would be similar magnitude to putting a 4x5 back on a Polaroid. Not impossible, but still a good deal of work to get right.

I'd get ahold of Minolta or Rollei or other 16mm cartridges and see how hard it would be to modify the camera to make one of those fit.