I'm playing in sandbox mode and am bumping my head into the maximum capacity. This seems like the kind of thing that would be pretty moddable, but I'm not seeing any to do so. Does anyone know if such a mod exists?
That's actually not a mod but a core game unlockable feature locked behind the Patreon password. I don't believe any modders in this community would circumvent that as that is one the things that is a bonus for backing Maverik on Patreon and contributes to him being able to continue to make the games we love. If you back him on Patreon, you'll get the password that you can enter in the start menu and select "remove population limits".