Is that a volunteering post for getting it rolling?
I think what the project needs is initiative. Someone to get it rolling, but probably also someone to keep it on track. I like Truthy's suggestion of a Bumble manager, and still like Narz's idea of a small test run.
We also need an item, whether it's a journal, camera, abominable snowman, or something else. I think I saw Bumbles for sale in a local drugstore about five years ago, but the closest I found tonight is this Bumble-style dog toy, which is 9 inches long (what was the original Bumble? similar or slightly larger?):
https://www.amazon.com/Rudolph-Rein...BMZTV/ref=dp_prsubs_1?pd_rd_i=B09KDBMZTV&th=1
Another candidate would be one of IKEA's plushies (
https://www.ikea.com/ca/en/cat/soft-toys-18740/?page=2), which have the advantage of being resupplyable in many places in the world should one go missing. Many of them are a big large for reasonable postage rates, but some are smaller, such as the giant panda (12 inches,
https://www.ikea.com/ca/en/p/kramig-soft-toy-white-black-90221318/), the gray-and-white cat (9 3/4 inches,
https://www.ikea.com/ca/en/p/lilleplutt-soft-toy-cat-gray-white-60260453/), and assorted miniatures (5 1/2 inches,
https://www.ikea.com/ca/en/p/djungelskog-soft-toy-assorted-designs-80402847/). Alas, the stegasaurus (19 inches,
https://www.ikea.com/ca/en/p/jaettelik-soft-toy-dinosaur-dinosaur-stegosaurus-40471220/) might be too large.
If we need a test run of something to mail around to see if candidates can successfully mail an item to the next person, I'd be happy to start mailing a Buffalo subway ticket around the world. Maybe with a nice sheet of paper about the journey that we could each sign before mailing on the subway ticket, so it's still kind of cool to receive but not as disappointing if it goes missing over the Himalayas as it would be for the actual item.
Or maybe postcard + letter would make more sense? Send a postcard of somewhere near where you live, along with the letter, the next person signs the letter and swaps in their own postcard, keeping the first one as a souvenir. It would be a little extra effort relative to the green army man/Buffalo subway card as it would require procuring a postcard, but that might be a better test for whether someone is likely to continue mailing on the yeti, which also requires a bit more effort than just putting a stamp on it (due to being package class).