My suggestion is one born from the loss of Greenery surrounding my base. I think it would make a very large impact on the construction of bases with the introduction of placable Trees and other assorted Greenery with having them confined in a planter. The placable trees could be labelled as Decorative like the planters and constructed in the Artisan Table.
I understand that this would have an impact on the performance of servers and private worlds, but i would the suggest the introduction of a spacing system a lot like the spacing between Tier 3 shrines. So that players would have to be smart and have to space the trees out. Even if having spacing is a bad idea then make players have a set amount of trees that they can place.
Just a Thought … XD