"*Firstly, unblock IPs that geolocate to countries where we lack contributors.Yes we will get more vandalism in those countries, but far far less than if we also unblocked all IPs in countries where we have lots of editors.*" -> That's not as simple as that, as the whole Wikipedia Zero Angola debacle has shown perfectly well - > at some point, the situation with piracy and vandalism coming from Angola W0 IPs was so bad that pretty much the whole country was hard blocked. I put a number of filters on place in order to monitor those editions on wiki.pt, and the result was that basically 100% of the editions coming through those IPs - and even accounts using them - were either vandalism, piracy or absolutely hopeless newbies who had not the least idea how to edit, without any means available to teach them - and without the least shred of interest from who was coordinating that W0 project in teaching the few goodwilling newbies the very basics of edition. This was clearly stated at the time by the WMF representative, it would have to be us, volunteers, who had somehow to find some way to teach users in Angola entering the projects from their cellphones (which is basically hell on earth even to old, seazoned, wikiwise rats like me and many others I know) without even access to talk pages or alerts or whatever how to edit Wikipedia. The obvious result was that shortly after that problem began, pretty much the whole country was blocked in a number of projects, including wiki.pt (not covering registered users) and Commons, and then, at some point, globally blocked on Meta. That was basically the end of the Angola community that had been forming before the W0 program started, since, if I recall correctly, the few users that existed were generally blocked at the time the global block was implemented, and asking for an IP block exception is very far from being an easy process, especially if you are using a cell phone, which was generally the case over there.
Anyway, IP blocks* per se *are not the problem here. It is perfectly possible to block anonymous access, as we do at wiki.pt, and allow (and encourage!) registration of new users, allowing for a much productive and much less frustrating Wikipedia experience - where newbies can find help in many ways, including at the new mentorship program, which works fairly well, and actually engage with the community in a productive manner from day 1. The problem are those global blocks that do not allow new users to register, and often not even registered users if they have not sysop access or are not otherwise IP block exempt.
Best, Paulo