Some of the concepts you noted - specifically #1, #3, #3b, and #3c - form the basis of some of the stuff that the IndieWeb participants discuss/work on; see https://indieweb.org. In fact - and i think someone else might have already mentioned these guys - https://micro.blog already provides such a paid service. (There are free features of this service, but IIRC the paid parts fulfill some of the items you noted above.)