from playing last night (and i think that was the 1st time i've actually played the map too come to think of it), I had a couple of thoughts i wanted to make:
i spent much of my time around final (probably due to being on red for 2 of the rounds and the low play count), as a result i can't really remember anything distinguishing in the earlier areas. that's likely due to the fact you've not fully detailed it yet.
the last area is definitely memorable in shape and form, and I do like it from an asthetical perspective. However, I think on a largely populated server that much water around the final point won't work in your favour. Water is generally a lot like lower ground in TF2 with the added disadvantage of a speed debuff, and an eventual damage over time.
I think your idea of making the water shallow enough to walk through is a good idea (perhaps 32 units though), however it'd be good to also have deeper parts as people associate large (horizontally speaking) bodies of water with extinguishing potential.
- perhaps have the area near to the fountain/final be deeper, using a displacement surface to smoothly curve it down.
another issue i noticed is that the upper balcony that looks out over the roll forward ramps. as a sniper i had an unprecidented view both of the doorway that the cart passes through and of much of the area to the far right (where there's a flank path for red). on a highly populated server that area will be hard to dislodge snipers from as the only access runs right past red's spawn door.
finally, the chickenwire/metal wall/fence thing just before the cart makes the turn into the final area is a real nuisance. maybe it's just me, but i feel that as much as possible there should be space on both sides of the cart. It's not majorly bad as it can be seen by players as they push the cart towards it, but still is sort've annoying.
also due to small playercount i can't really say if it was that important to gameplay. is it supposed to give blue more cover or red more cover? if it's for red, i'd say it's safe to remove it, since i'm guessing you'd rather the big final battle/holdup to be on the and around the ramps themselves rather than at that last turn.
from the point of view of scaling, i'd say that from what i can remember of generally playing i didn't feel i was being kept too far from the action at any time, although i do vaguely remember getting lost and having to backtrack quite a bit through buildings and then a shallow river with waterwheels. it felt that when i took a wrong turn i had to backtrack all the was back to the far side of the river and waterwheels before i could find a path back up to the payload track. (if your map hasn't got waterwheels on it then disregard as i must be thinking of another)
people might be feeling a scaling issue due to the large open areas of visible sky - this shouldn't be an issue once your detailing and skybox are in place thouhg.