i think about these things quite a bit.
Im more interested in building ones that can exist within our current system that allow people to flourish while simultaneously removing power from the incumbent system, in a way that will produce better outcomes for the populations within during the decline/collapse.
Its worth it to start at a human and tribal scale then scale up from there and iterate.
the top down models are failures best to let them fail and hasten that process while carving out some refugia that provide standdard of living for participants in them while establishing "best practices" that could be rapidly franchised out as more people want to exit the system as much as possible.
one of the problems people dont want to talk about is people abdicating personal responsibility and societal coordination to sociopaths out of sheer laziness and apathy. Nothing good works unless people want it. and people seem to be willling to trade any amount of freedom or justice or even money away to avoid the tiniest bit of inconvenience in the moment.
Best thing to do is hunt down other people that want to build alternatives now and start working with those people , fuck everyone else.