It's worth noting that some of the groups you mention are motivated by a general opposition to rent seeking developers, and would be perfectly amenable to a 6 unit resident-owned coop in the same location.

Nobody ever says "I just don't want a new housing unit there". Every single one of those groups has some kind of justification for why they don't want new housing near where they are. Some say it's to prevent "Rent Seeking Developers", some say it's to improve the quality of local parks, sometimes it's because the unit they are replacing adds some "special character" to their block. In the end though they all have the exact same goal and same effect. It's all NIMBY bullshit, everyone is for affordable/ new housing unless it impacts them in the tiniest way, then suddenly they are against it.

A big one is they don't want additional underground parking in their neighbourhood which means more cars. Of course cars are evil and they should not exist or be in someone else neighbourhood, parked along side-streets next to bike lanes.

Better yet keep those cars in the suburbs! But also suburbs are lame and we make fun of them (I would never be caught living there!). But yeah back to why I dont want more housing downtown... /s

Are those residents going to build that 6-unit themselves?

Yes actually.