Seriously Sergis? Dustbowl and Goldrush are not "basically the same map." Don't use that terrible generalization as evidence to support your idea.
There is no reason to nobuild anything in a map (sans a couple engine-related exceptions). If that's your way of balancing a map, you're doing it wrong.
I'm too lazy to read into what your problem here is, Hanz, so I apologize for not helping you out individually.
1-1 blu spawn area: not buildable
1-1 point area: low ground path with high ground paths on both sides, defendable building at the far end
1-1 to 1-2 transition: indoor tunnels, one of the paths getting quite close to point
1-2: different, although base layout is the same turning right
2-1 blu spawn area: buildable, transitions to 2-1 through a ditch
2-1 point area: large building on the right with narrow passage at the back of it, some building on left, area itself rather long with another building at the end of it, right turn with easy position for a safe engy nest after it.
2-1 to 2-2 transition: main path exactly the same shape
2-2: area with a building in the middle, a path going right through the middle of the building, building interiors have access to said path and give high ground
3-1 blu spawn: buildable, larger than 2-1 spawn, has a flank path
3-1 area: rather different, although shares the same notion of having defendable highgound position very closely to blu sapwn exit
3-1 to last (3-2 in goldrush): narrow path with a high ground path following it, gets wider right before final turn, has high ground/niche on left for attackers to hold there, has small "bunker" basement thingie which is mostly useless
last cap: underground lower flank path on the left, drop flank on the right, good position for the sentry nest flanking attackers from the left.
both maps are essentially different executions of the same idea layout-wise. gameplay differences stem mostly from different gametypes and different individual building designs.
as for nobuilding, i hate nobuilds for the sake of nobuilding. what i'm suggesting is badwater-style spawnroom with spawning area and some nobuilt indoors area afterwards.