So I know this Idea will probably never be looked at by Reaper, but I think its worth Discussing.
My idea foe The Dark Forest is a set of Modular and monolithic set of trees, that can be used for the majority of campaigns. It would consist of a few smaller trees that can be used as regular scatter terrain, these could be made to allow the clusters of leaves to be removed. Some larger Landmark trees, think the Tree of Despair, small tree houses, trees with nests, or hollows. Then a few large multi part trees that have parts that can be swapped out, such as an elven houses, shrines, or maybe even a nest for a Roc.