So how is an alien used as a weapon?

Seems quite outdated and futile.
Probably.

Any new engineered virus would make a much more effective tool.
Agreed.

It's also hard to handle n slow to deploy.
Maybe seemed like a good idea at the time.

Saddam had better wmds than aliens.
Turns out he didn't.

You drop a queen on a populated planet. The queen does its thing. The whole planet is being overrun by xenomorphs. Troops that would be needed elsewhere have to be sent to the planet. The military is stuck on the planet for several months (or years).

This was always such a stupid plot point that they pursued in literally EVERY media of the Aliens, Predator, and AVP storylines.

It never made sense to me.

Only the Predators' aim to utilize the queen as a breeder and humans as fodder (or prey) made sense to weaponize the xenomorphs. Otherwise it just didn't make sense.

It's about as effective as military raptors used as assassins (ala Jurassic World).

It's so stupid it's insulting.

Still, the idea could be salvaged as a population-control device by Predators. And had that been the story direction they went with, it could have opened up a lot of huge story opportunities. Unfortunately, writers with talent don't exist in Hollywood or are the ones never tapped to adapt a script for a screenplay.

I always interpreted the "Bioweapon division" line as multiple possibilities.

There is of course the first thing that pops into your mind, which is deploying actual aliens as weapons. That is indeed risky and not very effective - assuming the people you are attacking have guns... it's does not sound like a viable strategy.

But there are other ways. Mainly what I think would be most realistic is to analyze the structure of the aliens. For example the acid could be analyzed, synthetized and weaponized. Or any other material they are producing can be synthetised then used in bombs, chemical weapons, etc.

Even as a kid when I first saw the film in 1992, I thought more along the lines of creating new weapons / upgrading existing ones with alien material - and not really about deploying the actual creatures in war.

reproduces quicklys. in high dense population it reek havoc.

I think they used the term "bio-weapon," so it sounds like they planned to use them as attack dogs, but unlike in "Alien," "Aliens" showed the xenomorphs as stupid. The only reason the Colonial Marines lost was because they went in with no ammo and then they ran out of ammo later. They were doing good against the xenomorphs one on one. One thing I don't like about "Aliens" is how Cameron made them dumb animals that were easy to kill. In the first movie the xenomorph seemed very stealthy and smart.

I always thought there were two purposes, trying to control the creature and have it obey commands, but there was also the possibility of studying it, using it for experiments to develop perhaps a virus or something like they ended up creating with the human-alien hybrids in Alien: Resurrection.