If I understand correctly, you are talking about stretching the image over a longer piece of film (mechanically, rather than optically), then compressing it back to original size.
I'd love to see if that can be done mechanically (the recompression). I've certainly seen the stretching effect when you use you wrong gear. I learned early on in my career as a Cirkut photographer to always use the next larger gear choice if the picture falls in between sizes. That way people get ever so slightly thinner, rather than fatter.
Your idea is an interesting exercise, but if your goal is to put the information on a larger piece of film, then why not just use a larger camera? The #10 Cirkut Camera I use gives a 10 inch x 60 inch (or longer) negative. They were sold in sizes from 5" to 16".
I just recently sold my 120 Noblex and it was capable of very sharp 8x enlargements. Roundshots can give even larger negatives, but usually require an 8x10 (or slit scan, like I think you are suggesting) enlarger.
I do remember roughing out ideas with a fellow Cirkut shooter for a slit scan enlarger (there are commercial ones around, but not many). I seemed realistic at the time, but I suspect might end up being troublesome to get the kinks worked out.