I think 2 and 3 will hit other users. 1 I agree with to some extent, though it may remove the trickle of new users and won't stop existing bad people who join again.
Bad effect of 2 and 3 may be possible to mitigate by having email available to contact a mod if one feels one is being treated unfairly, also if you have a login that exists and is not banned you should I think be able to bypass 2 and 3 automatically.
But that is just me. Also maybe if possible one could put new users on moderation until a mod flips the toggle that they think the people is okay, meaning their posts do not show until a mod approves their posts, until they have their whole account approved. Not sure there is enough mods for that or if the forum software has that option even.
Also any of these things are less welcoming, but I do enjoy a forum that does 1, and I have not personally encountered trolls there yet. It is smaller though and has only one mod/admin...
Also to help detect multiple accounts one could have an ip log and see what users logged in from the same ip, though it is very imperfect for say families with multiple KB users (husban and wife for instance).
Of course all of this depends on what the forum software can do.