Long corridors will be combatted with Doors and changes in height... I haven't placed any "rooms" besides MS and Hives, so it all looks like a corridor facility.
Map Dynamically, Marines can "unlock" the map with weld points (changing distance relationships). a)Marines can also unlock bottom left for a surprise hive rush. If the aliens are aware of that possibility, 2 vents serve as their counter measure. b)Marines can unlock the double weld in the middle of the map, allowing them faster access to the farthest hive, again, with a vent as a counter measure + 2 vents that open with the welding.