Idea simple as pie. Top-secret underground base MUST have observing security cameras. So - if simply put idea - when aliens attack, they all are always visible to PHALANX soldiers/defenders (thought, if stealth aliens will be, they are exception then), and by that, base defense should be great and appealing game-play experience, neither like searching for damn last one half an hour.
Nothing fancy, no modeling or hardcore overkill programming. Just as visible everything on map, which, kinda, will work.
Of course, nothing like that shouldn't be on other maps, as it won't be interesting, but for base defense - I think, it should be great implementation.