It's a place that was touting their willingness to do such short strips, on Flickr. They do sound concerned that if all they get is one-off 36-exposure rolls it would be too much hassle. Sending them lots of rolls at once would be better, and my offer to send them 100-exposure rolls from my Canon bulk back had them even more excited.
Sending them the film in cartridges would be no problem. When I expressed a desire to get the cartridges back I did get some pushback but hey, those reloadable carts aren't cheap and probably won't be made forever! So maybe using used carts from a minilab or something might be a better plan.
Still trying to find time to shoot a bunch of test rolls so we can go through this whole process and find out if it's viable... from both a technical/hassle standpoint, and a cost standpoint.