You know I was thinking shields are quite sci-fi ish and would fit quite well into the natural selection universe. And shields can quite easly implemented and be cool looking on source.
What about the posiblity of having some kind of shield structure that would block off a hall way for a period of time. It would need to be balanced to it couldnt be used to just camp in base, so say it takes like 2000 damage and then it dies, a good use of a shield at the right time to stop the aliens from getting to a hive they are about to attack, or to cut off movement of aliens could be quite powerfull. It shouldnt be able to block huge areas so it would have a limit in size. It would need to have a fairly long build time, and would probabily need to be built right away or it overheats (so you cant just keep it unbuilt but almost built untill you need it then finish it). As a base defense or outpost defense it could be quite nice, when compared to turrets. Like a comm could block his base on the right side and then expand and get rts and hives to the left, with a warning if anyone attacks from the right. Could be used to help defenend a siege outpost a little while longer to take down a hive etc. I do think it should block both aliens and marines though, but can be recycled by the marines or killed by the aliens.
Overall I think it would add a lot of intresting tactical complexity and would look really cool.
