Vasquez doesn't start shooting and they bug out before getting attacked
In the movie, Vasquez has her own ammo and basically creates the conditions that blow the reactor and get most of her squad killed.
What if this doesn't happen -- they see the first cocooned colonist and then bug back to the APC.
Does this give them enough scare to tell Burke to fuck off and just nuke the station? Do the Xenomorphs still try to invade the control building? Do they just decide the colonists are all dead, call up the drop ship (or the reserve) and go back to the main ship?
It would be kind of cool if the evidence they have is enough to send for way more troops and equipment, and the bulk of the movie is some months later when hundreds of marines show up and engage in larger battles.