I seem to come across old manual lenses quite often in street markets, boot fairs, etc., such as the 28mm lenses I didn't buy a couple of weeks back because the focusing mechanism was stuffed. I'm wondering how difficult it wold be to adapt one as a tilting lens along the lines of Lensbaby etc. The basic idea seems to be that you put the inner lens mechanism inside a flexible tube with something to adjust focus and angle - the original lensbaby prototype used a bit of vacuum cleaner tube and I think a few springs and bolts to adjust angle and focus. You'd also need some way of working the aperture control and keeping external light out. Thinking about it, this is the sort of thing 3D printing would probably make quite well, since the lens tube and lenses and the bayonet mount are the only really precisely made bits. I don't have a 3D printer but to quote Top Gear, "How hard could it be?"
I think I'm going to try this the next time I pick up a suitable lens that isn't good for anything else. In the unlikely event it actually works I'll post updates.