@evan Well the question was:
"Who do you expect to see replies from when you post a followers-only post?"
So if you only expect to hear from your followers, without reply controls, the visibility of the replies to your post would have to be limited only to you, or, potentially, to you and mutual followers of you and the person replying, but not the followers of the person replying that don't follow you directly.
I think private mentions handle this well and rather simply.