Also to quote @Ghostse on this, one of the several methods of usage would be to insert silently and just let them wreck shit on a world or installation unfamiliar with them, then using combat data you have on them, send security/mercs to geek them using methods you devise. Deniability.
StarCraft gave us the script with how the Confederacy wanted to use the Zerg: You orchestrate an invasion, and then when your forces show up, instead of being oppressors they are liberators.
Arcturus Mengsk: I'm saying the Zerg are a secret weapon developed by the Confederacy. I'm saying you were all subjects of a Confederate weapons test.
Just as they destroyed Korhal with nuclear weapons to establish dominance a generation ago, they would use the Zerg to put an end to their rivals. Only this time there'd be no outrage; who could suspect the aliens were their creation? No, they'd be lauded as heroes for coming in and destroying the Zerg.
To give an example:
Imagine if the Cold War US military had some weird human-eating alien organism and they air-dropped some face huggers into Cuba. They let the things run wild, and then when Operation Banana Stomp kicks off to rescue the survivors, the US looks like heroes as they rebuild Cuba and take over.
The only reason the that 18 Cool, Buff
US Colonial Marines got rocked by the Xenos was because they weren't able to actually fight the xenos due to the hive being in the reactor.
Along with the other things you listed, there's a lot of plausible reasons why a Mega Corp would want some Xenomorphs. The issues past Alien 4 are that its increasingly retarded for people to try.
I'm also going to point out with Burke:
Burke had no idea the colony would be nuked from orbit.
His assumption was the colonists would get his samples and no one would be any the wiser. When the colony suddenly went dark, his assumption was the marines would take care of the threat and he'd still get his samples.
Upto this point, the expensive-ass colony equipment would still be intact. Even if everyone in the colony was dead, they can get more people.
When the bughunt went wrong, his next priority was to make DAMN sure to get off with the samples because he knew his finger prints were all over this, and if he wanted W-Y to protect him he was going to have bring them something worth paying off the survivors of 150-some people, and even if its just for acid blood a xenomorph would almost certainly do that.
Burke existed just be a 80s Corporate Raider stereotype, but when your motivation is "my personal gain. all other considerations secondary. everyone but me expendable." his actions make sense.
The issue is that because Burke was such a good character/villain and given an excellent performance with such positive fan reception even though he's scum, every other lazy ass writer tries to make a Burke Donut Steele and it doesn't work because they just slavishly follow the character's story beats with raised stakes without trying to make their character make sense.
Now some decades later, its some "black goop created by alien terrorists that also seeded human life too somehow" nonsense that I'm disappointed isn't a "alien nanomachines son" kind of meme. With several "totally not xenomorphs bro" creatures like that weird human looking xenomorph hybrid thing with the bloody leech face that is never once mentioned by name in the movie but all over the trailers and only kills one person before fucking off for the rest of prometheus. Just to be upstaged by a giant starfish that kills the alien terrorist.
Prometheus was one of the worst movies I have ever seen. Zero tension and just a boring space roadtrip with some zombies in it. Not a single actual Xenomorph and the protomorphs were barely even in it. I refuse to believe it can call itself an alien movie.
Necroing, but Prometheus was all style and no substance. The tech designs were pretty cool, performances were good (characters were pretty bad, but the actors were good) but the story was just utter garbage.
Having the Engineers/Space Jockies be "big, pale, bald humans" is one of the dumbest, most retarded decisions I've ever seen on film. Its so fucking retarded it goes back and makes the whole sequence in Alien also retarded.
Regarding the retarded "black goo" scene, the theatrical version without the whole retarded ceremony I thought that the story was "Space Jesus" was on the alien planet, saw the other engineers were about genobomb humanity, and sacrificed himself to unleash xenomorphs to stop it. Which I still feel would be a better story and more inline with the retarded Religious shit Scott was trying and failing to cram in.
And regarding the Alien Lifecycle, in Alien/s I got the impression that the Xenomorph in Alien was.... if the queen of a bee hive dies, many times workers will eat royal jelly and turn themselves from infertile workers to fertile queens. And then there will be a civil war where all all but one queen is killed (sometimes the colony will split but usually its a death match). So I just figured if there had been more food on the Nostromo, the Alien's task would be find a nest, coat it in resin, then work on creating a Queen egg. Otherwise, since the crew was small, just creating some more eggs to wait until they were found by some victims with the right conditions.