@baris yes, this was our method; however, there have been many real new users who wanted to use those fields, and it was taking a lot of time for us to fill in their info manually, so we had to abandon this method.
I know it is blasphemy to reply/reopen an old thread, but I think I have some sort of workaround for this. Say that per-category header warning message is 1) not going to be as native functionality, or 2) still waiting for plugin for that, I think a pinned thread atop all threads would suffice.