How would it work if you wanted or even needed to withdraw? Would a new version of the client need to be released, removing you as a default feed and moving other shareholders that are subscribed onto a different feed?
There should probably be a way for data feed providers to exit without requiring a new version release, removing them as an option. Like maybe the feed provider could enter in some setting, which triggers a pop up window in all subscribed clients letting them know that they need to select a new feed provider from the list because the one they are currently subscribed to is retiring.
The list would need to be able to auto-update as well. Maybe the setting you entered in above also triggers the removal of you as an option in everyone’s clients. I don’t know. I’m just trying to give ideas to the dev team so they can figure something out.