tpope/vim-projectionist — pull request #20 by mtscout6 (2014-05-27 17:09:42+00:00)
Title: Added prompt if alternate file does not exist, asking if you want to create it

This does not have to be the final acceptable solution for #5 but this is what I plan to use until something is figured out. Instead of blindly creating a file, and instead of saying absolutely not I'm leaving it in the users hands to decide whether or not to create the missing alternate file. I'm open to suggestions here!