I would personally like to see the human ai able to handle some minor issues itself. Not a direct competition thing, nor even a second group of people, but the humans on the terror missions the aliens keep starting.
Since my human weapons can do considerable damage against an alien, often killing them with a couple hits, even with weak weapons, I suspect some humans will also have such weapons. 1 hit will injure aliens, and possibly even kill them, so considering humans greatly outnumber aliens in any of the battles, it would be nice if the humans could do something, anything to try to protect their own lives.
Even the weakest guns I could find did a fair amount of damage against the aliens.
So, in summary, I don't like the idea of competition, but having humans be a bit more useful would be great! I mean, the only times the humans actually do anything useful is when they are shooting at you after they've been infected. And at that point, they *can* hit, fairly well, so I suspect they can hit before they get infected too..