Also interested in subs- do worry about dilutive effect on community.. might over-complicate things logistically but I wonder if there's a way to vote (in sats of course) them into existence to see what might have the most engagement rather than creating a bunch of mini-subs with zero community.

Indiehackers (although the community has little real engagement and seems to be dominated by all self-promotion) has a "groups" feature where the proposed group does not launch until a certain number of people join the group.