I think the only ulterior motive in sending a green lieutenant was so Burke would have more influence over the mission.
In hindsight, the Apone's squad got extremely unlucky when they found the one colonist who hadn't popped yet. If that hadn't happened, they may have never awakened the aliens and could have conceivably withdrawn to the APC without firing a shot.
Satisfied that all of the colonists were dead, they may have pulled out entirely with Burke's specimens in tow (whether or not Ripley objected) and returned to Gateway.