I'm not sure if anyone has done anything like this before, but I have created a simple tree farm that is very easy to harvest. My design only accounts for having two trees but can easily be expanded to house as many trees as you want. As you see, the seeds can be planted on 1 block wide pieces of dirt. The box around the saw on the left is purely for storage so careless nubs don't accidentally jump in. The trees then grow up through the slots. Once the trees are cut down, they will hit the walls and all the wood will be neatly piled at the bottom. The one block of wood stuck at the top is only there because the walls weren't high enough. Once they're cut, you can just pick up the saw and throw it at the wood to cut it up into planks. To put the saw back you need to jump up and throw it into the box. The whole process (from un-felled trees to planks of wood) for this farm only takes about ten seconds. If you see any room for improvement, let me know.