ZenTreehouse
This mod adds a static treehouse to the game.
It's not a buildable or craftable treehouse, it's a static building, which means it must be placed in the world using a tool like DayZ-Editor.
Once it's placed however, it does contain a doorway and a securable ladder so if you have Build Anywhere enabled on your server players can secure this as a small base - perfect for lone wolves and small groups.
There's also an alternative model which has no structure on top, so players can build their own little base if they can find a way to get the logs up there.
It doesn't have a config or types entry - you must place this object using the init.c method or some other method for spawning static objects in-game at server startup.
Personally I just place a bunch using the DayZ-Editor along with a tree in the tree hole (bldr_plnt_t_FagusSylvatica_2d_summer works great), export them using the init.c SpawnObject() method, and spawn them on startup.
There are guides on YouTube about how to spawn DayZ-Editor placed structures in-game so search on there for guides if required.
Land_ZenTreeHouse_Ladder - Treehouse with a structure on top.
Land_ZenTreeHouse_Bare - Treehouse with only empty platform on top.