I doodled this out real quick. Red/Blue lines are sniper sight-lines Assuming spawns are placed on the far left/right, each team would have way too easy a time camping the choke just outside each spawn, as there are no alternative routes or flanks. This could be easily solved by converting each of the buildings by each spawn into a sort of "teleport station", for an alternate route to the middle of the map. Even if you don't want a teleporter because it gets people there too fast, consider making maybe underground tunnels or something, because the camping situation would be really bad with only 3/9 classes being able to make it over the trees and avoiding the choke easily. The casino would be a great place to hide secrets and whatnot, as it's close to the middle of the map, and therefore people would naturally fight for it.
Anyway, this is just a basic idea of what I was thinking, tell me what you think etc.