It works out if high density housing is built and then all sold as condos. People could pool together and buy land as a coop-style group, and then develop it as high density housing. But then its facing organizational hurdles (coop-style orgs don't have the best outcomes) and the whole thing need to survive years long timelines (to design, permit and build) while staying focused to avoid cost avalanches. Good luck!
I don't have an agenda in this (unlike other commenters suggested) and would love to discover a better way of doing all this. I think the current system is flawed but I don't hear convincing alternatives. And what's there right now is better than a feudal system, that's for sure... Hey, back then, Lords were owner occupiers! How has that worked out for the peasants?
Hence why I think the issue isn't about taxing more for stuff like "not owner occupied", but more about the opposite: make it faster and easier and cheaper to build high density residences. Then prices will fall and the affordable market will be served by smaller developers.
I'm sorry but you can't make more housing appear by simply raising the barrier of entry and throwing sticks in $INSERT_EVIL_GROUP's front bicycle wheel. Ultimately, things need to be cheaper and easier to build, and this will come at the cost of some people's freedoms (expropriating their land for redevelopment, displacing people for redevelopment, preventing bike shedding about neighbors' preferences).
It's easy to take a dump on so called rent-seeking landlords. But picture yourself becoming a landlord; imagine you're this newly minted, high spirited multi-family property owner and you want to do good for your neighborhood without becoming a charity and ruining yourself. Then look at what your options would be. In many US urban areas, there's already a lot of regulation in place that would drive you mad in your inability to make things better for your tenants and yourself in a sustainable manner. The rules literally push you into what you're seeing in the rental market (crappy apartments with high rent).