Hello, I'm the creator of said cancerous map. I do apologize that my creation gave you cancer, I assure you, killing you was not my intent.
Nevertheless, I'll answer your bullet points with my reasoning:
You came to that conclusion by looking at the map scale, but not the actual play space, and certainly not the relevant play space. The relevant play space isn't any significant amount larger than standard Tech 5 maps.
The Ore Truck takes a while in order to provide an opportunity for Infantry to destroy it and have it be noticeable. If the path was short like more commonly the case, destroying a truck only delays the income less. This is proportional to the travel time. To prevent economic blackouts, the dual Ore Silo keeps the game going until a team decides to take them out... If that occurs, an economic blockade becomes a real threat, and this is how you're most likely going to win the match.
So first you complain that the map is too big, and then you're asking why some space is inaccessible by normal means? You're weird.
Siege once offered about double the available play space than it currently has. The castle roof and interior access were axed in order to trim down the map. A lot of play space got axed to leave mostly only the relevant play space. Initially a bonus area (map secret) made the cut, but was eventually also axed. All this axing was for this triple purpose:
To utilize a smaller development budget. Creating assets to occupy space takes time.
To improve performance, less areas to render means more frame rates.
To streamline the map, so that players do not get lost in areas that have no meaningful impact to gameplay. The purpose of APB is to destroy the enemy base, not to play hide and seek.
Adding more space simply isn't an option unless gameplay changes demanded it... In Siege's case, that is unlikely unless @Pushwall gets drunk one night and decided, in blood, that Siege needs Naval combat, for... reasons.
As for ghosts... They are a byproduct of inhaling toxic gasses. You don't actually believe ghosts exists? Man up soldier, and go inhale those gasses of illusion!
I happen to enjoy a good rain, especially during these hot summer days. Weather helps set the mood in a map to be sure, but rain being a cause for depression? You must be of fragile mind to get depressed by some water. You'd best avoid places like, you know, lakes, oceans, even your home water tap.
A common point of feedback in APB is uninspired or identical base layout design. While the Allied base on Siege isn't really special, a bit more work went into the Soviet base layout. The result of attempting to make it stand out was the lowered War Factory, expanded base tunnel, and compact building placement. The helicopter landing pads are an extension of that idea, and makes Soviet aircraft climb while clear from the base (you don't take off in an aircraft near a building, typically, due to the hazards caused by flight malfunction), and further more, the outward layout serves as a supportive extension for an adjacent Airfield, should that be enabled on the map.
Naturally I'd have put more detail into the map, but even with visibility culling, the performance is absolutely pushing the current limit of W3D.
Either way, if people truly wish to remove the map, then it is for @Pushwall to decide. I delivered the level, and he maintains the entire APB project. Suffice it to say, Siege was my last "new" contribution to APB. The upcoming HostileWaters revamp is my final contribution, it always was. I feel that I've lost touch with what players of W3D games want, and it'd be a waste of my limited time to continue creating undesired assets. Whether or not this will also mark the end of my working with W3D entirely is still up for me to determine.