Get Tags by Author — Not Tags from Post by Author

I’m looking for the best way to store a tag’s relationship with it’s author/submitter. I’m wanting to build a front-end ui for member tag submission.

I had to previously setup a new table for tags and relationship to get the right result but am looking to integrate it with less modification.

Say I add a user_id column to term_relationship: How bad of an idea is that? Would any built in methods or hooks work with it? Any issues with applying the a tag multiple times to the same post — but by different users/submitters?