If number one is ever (heaven forbid) implemented, Admins MUST have a way of prohibiting it from being used on their site. I don't care if users ignore each other, but I will not stand for users determining who can and who can not post on the site.
As for number 2, why in tarnation isn't it done this way to begin with? If a user is on ignore, everything from that user shouldn't be displayed to the person. Posts, topics, etc. Should all be hidden from view.