First, I'd love to see more weed plank builds, such as plank floors (to give it a "hardwood floor" look). And maybe some plank roof parts for that rustic log cabin look. And grass floors can go over top of weed floors like carpet.
Second, what about decomposing parts? Like with parts for a house? After all, armor and weapons need repairs, why not parts? After... say... 1 in-game month after building a house part, the grass parts turn yellow and the weed stem parts turn black. After 2 in-game months, the part automatically destroys itself (decomposed). But you can repair the pieces before that time. Or you can make it last longer by using sap sealant.