Based upon that playthrough we just had I'll make some comments on how the map could be improved.
First thing is the alien base location is horrificly vunerable to death from above, watching marines chuck grenades down simply isn't fun. This might be solved in future once people get used to playing the maps and move the alien base about rather than leaving it where it is though.
The vent sysetm into the human base from above all the way back to the human base needs a bit of a rethink. Bulky aliens can't fit up there removing their ability to attack from that direction and even more terrible, if you evolve whilst up there you are fucked as you can't escape. And speaking of escape, the big pipe leading down lends some problems to the aliens with it's size as with their inertia it's actually tricksy to drop down, I got caught a few times on that rim half way down it unable to fall down the whole due to the speed and got pumped.
Of course it's horrible when you look at the other approach into the human base, long corridors lead to lucy spam and with there being only one effective way in it's hard to distract and seperate human forces leading to fairly significant levels of impenetrable firepower from one location.
I've not seen it yet but I can imagine it won't be too long until humans try exeprimenting with a base in the big room by the elevator, it's easy for them to put a dense collection of defense structures at the teleport point sealing that off and since it's right next to the slow elevator larger aliens will be forced to take they can deny aliens this approach all together. That would force aliens to use the other path which I've already mentioned is a potential death trap and how well that could be defended all depends on how the points can be allocated.
The circualrish room with the vent exit could also do with being simplified to make wall walking easier, especially since a human can lodge themselves in some of the beams which makes it very hard for an alien to get close enough to them to hit.
Anyway potential solutions:
For the pipe with a rim in it, widening it will help, and humans will probably love you if you remove one section of the ledge and put a ladder on it. This lets them escape rather than trapping them which makes them happy and leaves a notch to aid in aliens trying to scamper.
As well as this if one end of the the horitzontal pipe could somehow be connected to the rest of the map it would probably be a huge boon. Even a simple large hole in a celing somewhere so tyrants could escape would be a big improvement. Better yet might even be connecting it to the map with ramps so larger aliens could actually get up there though you would still be leaving the tyrants out.
