lessen taxes?

The impact of tax policy in Malthusian eras is hard to determine--it might adjust the population size, but probably not per capita income. But it does seem like one could convince someone that urbanization is important, and they should focus on solving the city-level problems of sanitation, trade, and economics, which were approached only haphazardly at the time. Convincing them to move to an Imperial Free City and spend their efforts sanitizing it / developing institutions that keep it clean might be useful.