Stricter permissions and/or better measures for direct messages

Hi!

I run a medium server that is used mainly for language learning. We've decided long ago to require new users to introduce themselves in order to gain full access to the server (no strict requirements; just a sentence a bit longer than a "hello"), requiring members to put in some effort. This has overall been very successful at deterring trolls and such, but we still have the issue of scam accounts joining.

These people obviously don't send an introduction and thus cannot really participate in the server, but they are still able to freely DM others in the server (who have not set their privacy options otherwise).

I'd like to request a feature where this ability can be set as a role permission, where if they do not have it, they may for example only be able to message moderators/admins unless they send a friend request. Another, perhaps easier method, would be to have an additional warning show when they open the DM window with the user, that the person they are communicating with has not interacted in their common community/-ies, and that one should be extra wary of ill intent.