Hardcore Xeno fan here, saw Hiztaar and Faðir Allra talking about this... Here's their original comments and my reply beneath:

Faðir Allra 3 Nov @ 11:42am
BTW: I am currently working on a little project to implement the Infestation disease.
For now I have adapted the WoundInfection to act a bit faster. It is also not tendable, the body cannot immunize. The next step is to make it removeable by surgery. Oh and it is absolutely lethal if not removed, like the actual infestation works in movies.

Hiztaar [author] 3 Nov @ 2:35pm
Disease is not much of an issue for the life cycle.
1. You must have eggs that open on close proximity with a pawn or animal
2. The egg must spawn a single facehugger
3. The facehugger must touch the victim. Once touched, the helmet of the victim must be destroyed and replaced by a "facehugger" helmet that cannot be removed without killing the pawn
5. Setup a timecounter for chestbuster birth (disease system, pregnancy system or custom made...)
4. After a certain duration, the FH falls dead and the pawn wakeup with hunger rate x5
5. After 1 - 24 hours of gestation, the pawn falls because of pain then die in the following moments as the chestbuster is born
6. The chestbuster is weak and must flee but in RW it can be oneshot and do not represent a threat at all. The only interesting thing to do with it is to allow it to "disappear" in vent conduits or if it reaches the outdoors.
7. Surgery cannot remove a chestbuster without killing the host. That's life.

So, let's see how muddy I can make this water mwahaha!
1: can they be designed like an IED or othersuch trap?
2: they could self-destruct, or make a 'useless' structure/prop of an open/empty egg
3: as an aggressive pawn, they could have specific rules to attack the head and (this is where my little XML knowlege falls apart) have it spawn a status similar to poisoning or food sickness.
4: this could be part of the 'infection', similar to fiberous mechanites (breathing restricted, conciousness etc)
5: err... can't add anything here since Hiztaar has that pretty all covered from every angle.
5-2: Possibly another condition spawned instead of instant death (this condition would be incurable and your only option would be to euthanise via cut). First person to say what the tooltip should say (in line with ALL alien movies) gets the pseudo-honour of saying it was their suggestion
6: This would be improved considerably by having 'fog of war' on for the game. The Burster should be SERIOUSLY hungry and probably will start by eating it's 'parent'. once it reaches a certain part in it's lifecycle (two days in-game? Less probably) it can begin to shed it's skin. How fast it does would be up for debate
7: eeeh... this is a bit of contestion... The games suggest that it's impossible, however the comics and movies suggest otherwise. It also doesn't make sense that the burster would have any toxic components at all until it's obvious unhealthy exit method... The facehugger however, that's a totally different story entirely! What happened Bishop? "They killed him getting it off"

Also, I would want to discuss the possibility of PLAYING as a Xeno! Imagine if you have a queen that produces resin and you have to use that to build your 'hive' ;)