That is most certainly interesting. Perhaps everybody ends up in requests unless you have history of DMs with them?
If it were up to me, I'd let your follows (not followers tho) let you DM without a request and let requests just be mostly spam with the occasional gem or as you propose having an option to limit who can DM you. Both seem to me to be equally valid solutions.
nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z Thoughts?