You know, in addition to what Randdalf said, I've always found the final cap a little underwhelming compared to other good payload and A/D maps. For example, Dustbowl and Gold Rush's final stages wind through narrow passages until the last area, which opens up quite a bit. This makes it easier to defend, reduces spam for the defenders, and gives them a more "epic" feel. Same thing for Badwater, which goes from a medium corridor to a huge open area.
I don't know that it's necessary, since it's already such an excellent map, but if you get bored with other stuff you might consider opening the final cap quite a bit. I would probably take the final building and open it up, making it at least 4-5 times larger. You could have the bridge across wider, more like the width of the Dustbowl bridge. You could lower the floor and make the stairs switch back and the lower tunnel actually have stairs that go down (making it a good rocketjump platform as well). Some skylights on top would prevent it from feeling too closed in as well.
I think right now your best final point is on stage 1, where it opens up and is a reasonably sized area. I think stage 2 is fine in its current state. However, stage 3 feels much more claustrophobic and spammy. The design of the final room is pretty good, but people really don't see it much because it's so small and so little action happens there.