There are around 1500 towns in the US with population between 10,000 and 25,000 [1]
So it's not like this hasn't been done before. And sort of the ultimate chance to engineer the world you want to live in -- I'd think people would be really into it.
I know that YC has/had a "New Cities" initiative but I haven't seen updates in years.
[1] https://www.statista.com/statistics/241695/number-of-us-cities-towns-villages-by-population-size/