These are my few suggestions and ideas for HnH expansion. I'm sure some have been suggested, in which case consider my duplicate suggestion more of a popular vote.
Bridges:
New Skill - Bridge Building
*Rope Bridges capable of being traversed only by hearthlings and animals (not carts or wagons). Would require rope and boards, and perhaps some leather (fastening) and blocks of wood (anchors on either end of the river). It could require boat building or swimming, one would have to build an anchor point on either side of the river before the bridge could actually be built. This might require some sort of dynamic feature though since some rivers are wider or narrower than would allow for a single static structure. Rope bridges would decay relatively quickly due to constant exposure to the river and use.
*Stone Bridges capable of be traversed by hearthlings, carts, wagons, animals etc. Would require a lot of stone and have the same general principles of the rope bridge. Stone bridges would decay very slowly, but would be very labor intensive to build.
Bridges would give new purpose to road development between villages and may encourage more pacifistic behavior such as trade and communication. Boats would still be able to pass underneath, and one could fish directly off of bridges.
Tree Climbing:
This should be available very early on, but carry risk like swimming does. With low strength and stamina the risk of falling from a tree and taking minimal to significant damage would be high, but could be improved. Tree climbing could add a new dimension of foraging, such as birds, bird's nests, more bugs, new curios, tree saps etc, as well as more inclination to specialize in ranged combat. One would be able to fire ranged weapons from in a tree, but could again carry the risk of falling out of the tree at lower levels of strength and dexterity, which could prove highly dangerous if one fell out of a tree and down onto the ground with a wild animal.