I agree with a lot of what Mangy said, but I'll just post my own image since there's at least one thing I disagree with him on.
1. Orange arrow
So, as Mangy said, move the red spawn and C building back to open the area up. This will prevent instant scout caps and make it feel more vertical without actually making it so (by removing the rj from the outer ledge onto the CP).
2. Orange arrow
Move the blue spawn away from the doors. This will not only make it less complicated, but will allow engineers to put sentries outside the spawn area and have players see them when going either way. It will also cause teams to group together during setup more instead of splitting to the two sides.
3. Purple X
Remove this alcove, but leave the other one right by it. Mangy suggested removing both, but I think the other one provides an excellent ambush area for sentries, demomen, spies, pyros, etc. Also, you'll notice that the path from A to B on GP plays really boring since it's just a straight shot through. By adding open areas on the paths you make the gameplay in those tunnels a little more dynamic instead of just forcing players to run forward or back in them. I also think the one on the B/C path should stay. The reasoning with these two is that they're on the blind side for attackers, meaning they're natural ambush locations.
4. Green lines and blue X's
This is my big suggested change. I didn't follow what Mangy was saying here, so my suggestion may be the same or opposite.

The green lines are the walls of a unified central route on the map. Basically it ties together all 3 locations and eliminates two of the other paths (kind of). The blue X's show that those two paths would be removed since they're combined into the middle route.
The result is that there's still a quick path between A and B, and that there's two routes from A to C and two routes from B to C. It's just simplified so on the C side you only see 3 incoming paths and at A and B you only see 2 outgoing paths.
For comparison on GP you see 4 incoming (since the B paths are basically the same since they're so close) into C. On GP you have 2 outgoing from B (the two directly to C really count as 1 and the 1 to A is the second). You also have 2 outgoing from A (1 directly to C that branches into 3, and 1 to B).
Overall I think reducing the incoming paths to C will make things harder on the attackers while making it a lot easier for players to find their way around and communicate with each other.
Also, I like the changes you made to C. I think it'll play a little nicer, especially in competition, and looks impressive as well. I do think there's a slight lack of protected sentry locations, but I'm not sure where you can improve that. You do have a downward slope on both sides like GP, which are ideal and expected spots.
You also have the near ledge to catch people as they come over, but I think you could really lock down this point and make things hard for attackers by making an alcove under that front ledge. Something like this...
Basically, look where the green is. This would be an alcove underneath where engineers could put sentries that would be able to hit people as they dropped over the top. There's a tradeoff since enemies that rj overhead might get a slight boost from the sentries and be carried to the CP better. This is very similar to the overhang at Gold Rush 2-2, right next to the path. It makes things very hard for attackers without having to make any other changes to that area (although moving the building back is still a good idea).
I don't think this area is OP because demomen can still hit it from the windows on the side or from the ledge on the other side, plus ubers can attack by going down the ramp or taking the lower route from B.