I don't think that's wise at all. Technically you would have your root or admin user which can DROP or ALTER tables right? You don't want it at all possible for a user to get access to your database internals.
Why don't you have a separate table (at the moment that is)? If you require your users to have real database access (for another system or application) then you should still create a proper users table.
You can always write a script which will sync the data across from the internal DB users table to your application users table.