My vision would be something similar to the Radio Browser [1] which maintains a dataset (of online radio stations) used by several open source apps. When a user of one of the apps contributes a new station, it benefits all the users of the other apps too....
Would also be curious on folks thoughts on the licensing of such a collection. Does not seem like UG is paying any licensing fees for its user-contributed tabs, but it feels like if it was as easy as creating a public DB of tab files on GitHub, someone would have done it already....