I don't think that would be really possible for this elevator...since it's not a critical part of the gameplay does it matter or would players get annoyed at it?
Also, I'm having trouble designing a decent alien base for this map. Does anyone have some useful tips or ideas? (Do's and don'ts?)
At the gameplay.. depending how you make the elevator its probably a 1 in 100.. so i doesnt really matter
At the alien base,
make some tight places to stick the overmind or eggs/tubes/(insert alien buildable here)
make ledges... grangers like ledges
and finally.. maybe add like a L or a half loop hallway? would make for some interesting gameplay and building.
as for donts.. i cant think of anything

hope this helps