I think land assets should provide raw resources that could be refined or combined to make additional things, such as crude weapons or armor. The could also have various function based on structures placed on the land, such as research pods, greenhouses, smelting facilities, ect. Harvesting the land and using those resources would add some value to the plots, as well as being able to build structures to boots stats via research to boost mechanics, security, diplomacy, ect... you could tie the max population of a settlement to the land size + number of living quarters, for example