Put themselves into a queue where the moderators can decide which subscribers should now become posting members
I think, we should also give the feature to remove subscribers to empower the community more - for example, the community may grow too fast but later on they only keep those people who they think are more beneficial for the community.
I am having a hard time understanding what removing a subscriber accomplishes... also we can't remove our followers either. We can mute followers and we can mute subscribers ... seems like all the use cases are mostly covered.