Hi, Tuaam. I have some feedback about the two things you asked about.
When I come out of the base, I can see what you are concerned about with sightlines. I think that those are symptoms of having an uninteresting wide and open space that meets every player and class when they leave their fort. When you build a map for TF2 you need to design spaces that are suitable for each class, so you should avoid making big empty, featureless spaces where every class joins a spam pit. Continue your class-tailored structures and routes throughout your map, occasionally having them cross over each other so the classes meet. Look at Badlands and Doublecross mids, and Badwater's starting tunnel and think about how the play spaces are divided vertically, providing different play experiences, different class-tailored architecture and reducing the intensity of battles because of fewer participants. In your map's case, I think the solution would be to break away from building the exterior structures as islands, and making longer buildings which provide for a mix of close-quarters combat, and divide players. Think about how a spy or pyro would play there.
I think it would be easy for players to accuse your map of having a lack of height difference with respect to play spaces. That might seem confusing, because you have some islands outside with ramps, but at the moment players aren't required to use these ramps on their way to the objectives. They are just optional places to walk, but they delay the player from getting where they want to go, and in such a relatively small and open area, players might feel like the cost of time taken to use them is outweighed by the need to fight the encroaching enemy in order to survive. If you made these raised spaces part of the routes to the objective, players would take them, because they would be convenient.
Something else: When I leave spawn I don't know which direction is the intelligence room or which direction I should run to go to the enemy base. Don't rely on the outline of the flag for players to navigate. Signs will help but they should be used to confirm a player's sense of direction, rather than relied upon completely to tell them where to go. The structure of the layout and decoration should be the strongest indicators.