Removing forests for building space is a fine mechanic. As you get more buildings, you need more space. No problem.
However, by not removing the two sections leading to the side hills, a near impossible bottleneck is created. You can throw 30 clubbers and 24 seadogs at the center hill and almost none will make it up. Even with heals and stuns dropped. At max level, rifle towers on the hills make a near unbeatable defense.
To solve this, its an issue I think at high levels, attacking troops should be able to move through forests. Maybe at a reduced pace if you want to keep some benefits. If the defender wants to defend those hills, well, thats a good reason to remove the forests to place defenses.
IGN: kmb08753, Glory record, 7568