Then where do you propose that they be stored such that it’s possible to display them? I guess they could be in theme settings, but that’s actually still in the database. But having the 10 hard-coded reasons doesn’t solve how the reason will be connected to the user. I suppose a custom field could be used. That’s still in the database but wouldn’t require changing the schema.
Probably not. It’s very difficult to develop plugins for old versions. It’s also hard to install plugins on old versions of Discourse.