Earth and Water factions.

Folktails harness the wind. Iron Teeth burn fuel for their engines/smelters. Wind and Fire are represented. A lot of posted suggestions could be rolled into two new factions, representing Water and Earth. Some of these options might be global, but these factions would get better/cheaper versions, like aqueducts, etc.

Mud scuffers [Earth]- can dig up earth to remove/create new land mass. Can build Tunnels that go straight through mountains (or are built like paths, dealers choice). Homes cannot be stacked, must be on the ground. Substitute some material costs for new "stored turf" resource.

Wetlanders [Water]- Immune to flooding. Homes must be built either directly beside, or in water, or have water piped in. NO WATER STORAGE NEEDED, daisy chain water supply just like power. Can build pipes to move water upwards or into buildings, aqueducts for lateral movement. Better dam/levee/floodgate options, hydroelectric dam/levee tiles. Use wheat as a building material (straw roofs, etc).