I thought of these as well, but they still wont work either. It is still a hugely defensible spot. They can just peek around, do some damage and fall back, then switch attackers while the other heals up.
I would say remove the wall and drop the entrance so the sentry can attack the entrance if needed. The big cheese is the ability to shoot from there without the sentry hitting it. Maybe even raising the ground a bit as well so the change isnt as big, as big changes in map or structures tend to have downstream effects.
The way it is now only makes the area a kill zone in advantage of those occupying the supply room which, previously, was able to be cleared by coordinated attack from both sides. 1 side can be closed by 2 people, leaving 3 for the other which with the right team is plenty.
