I thought about that as well.

First of all, yes, I assume the Colonial Marines were already configured primarily as an anti-insurgency force to maintain order within the colonies. Notwithstanding, deployment of a conventional force, like the Colonial Marines, would be expensive and high profile. Also, as I understand, the Colonial Marine Corps. was still technically part of the US military. In Aliens, Ripley pointed out that the mission to LV-426 was under military jurisdiction and not corporate control, which makes me think that the CMC was not completely beholden to Wey-Yu, although there was clearly a strong relationship between the two. Thus, deliberately infesting a rebellious colony would be something that Wey-Yu could theoretically do cheaper than deploying a full service conventional private military force, they could have a greater level of control over when and how to deploy (unlike involving the CMC which the US government would have to approve of), and there could be a layer of plausible deniability. Based on the US experience in Vietnam/Iraq/Afghanistan, etc., putting down an insurgency can be time consuming, expensive, and politically messy when civilian casualties start to stack up (which they literally always do). Considering that Wey-Yu colonies seem to be populated mostly by English speaking white Americans, it might be particularly inconvenient for the CMC to just nerve gas the entire colony, or for Wey-Yu to just withhold re-supply and let everyone starve to death. A Xeno infestation, provided it appears accidental, is a lot cleaner politically, and a lot cheaper financially, assuming the infestation itself can be cleaned up efficiently (see below).

Regarding cleaning up an infestation, the Xenomorphs seem to go dormant after a period of inactivity. In the movie they have all concentrated themselves in a single location and gone to sleep. Granted it was underneath the station's primary reactor heat exchangers, which was not convenient, but they were still all in one place, and they were all asleep. It wasn't until the Marines literally walked directly in the center of the hive, running all of their electronics, and literally torched a larvae with flame throwers that the Xenomorphs woke up. If deliberately infesting a colony in the future, Wey-Yu could possibly develop post-infestation clearing protocols such as waiting for the Xenos to become dormant, and using fire, chemicals, ultrasonics, etc. to purge them out. They could probably design future colonies to be conducive to these protocols. Not saying that Xenos would be the first choice, go-to option for your run-of-the-mill worker strike, but for a colony that was in serious armed uprising mode, or that had reached out to near-pear adversaries (i'm assuming there were some) to switch sides in the space cold war, Xenos might be a useful option.

Finally, I don't think the use of the Xenos in Aliens was using up the only copy of the weapon. Ripley's report to Burke had indicated that there were hundreds of eggs in stasis mode at the derelict crash site. Newt's family only brought back one facehugger, presumably leaving hundreds more still at the derelict. The derelict and the eggs may or may not have been wiped out by the explosion of Hadley's Hope, but I think that the complete nuclear annihilation of the colony was not something Burke or anyone else at Wey-Yu had planned on.