Im not sure, I just think you should fill it up with something. There's many blocks you can use. And decoration you can spice the map up with.
EDIT: I have added an extra house a little extra terraforming making the overhead view now look as so If you would like to see a closer up view on the house and the inside look under here Spoiler: Here this is the inside the hole seen over there which has 4 different sections inside of it that aren't very long @Smiley and @DinoDuck wanted to see some more stuff so I'm tagging them to look at it.
This will be another Argentan. But in this case it will be even easier to get to the helicopter. Also the map is pretty much only a tree, which isn't too fun.
I'm not exactly sure on what you mean on it being another Argenten. On that one, it's nearly impossible to kill anyone on the helicopter. The same can not be said for any position on this map. Do you have a picture of that tree? I do not believe I am familiar with it.
Support. Honestly, maps don't need a LOT of detail, I mean it would be nice to see such improvements, but you also need space to run, this IS Infection afterall.
Using park our to get to a camping spot. Same in your map and Argentan. Except in your map, the parkour is easier, so more people will get to the camping spot making even more difficult for zombies to complete the parkour.
Since the parkour is easier and spread out, the camping spot isn't as powerful. There are other levels of the parkour that block lower levels of it. Furthermore, when zombies get to the spot, it's all over. At that point, the humans have almost no chance of survival, due to knockback and fall damage. They'll get hit off the tree.
You underestimate the 2-shot bows and multiple donors camping in 1 spot. Trust me, I have been playing infection for a long time, I know how maps will turn out.
Alright, well thank you for the input as @Teddy said, there does need to be room to run and the main focus of the map is the tree.