It's a future for socialn-like sites . We need intarfase for save/edit/delete/read custom user settings
Are you keen to make it for 0.9.12? I think it should be separate from basic config (cot_config table).
Does you mean common user settings (like user profile) or you write about admin configuration storage?
This is about things like preferences per user per plugin. E.g. "display sidebar" in "mypage plugin" for user X.