I too have been of the school of thought that; With no Queen present a lone adult will morph a host organism into a "super facehugger" or "Queen bearing" egg.
They may even make several of them, to guarantee survival of at least one. Survival of the species at all costs.
I know some feel it should be an egg for another adult warrior, but to me, it makes more sense that it would be Queen bearing.
I do not take into account that the Queen was not a concept then. Sure she came later, but she can still fit in with it nicely.
The way I look at it, all aliens are capable of creating the "spore" that grows into an egg by converting existing organic matter in the egg cells.
The Queen is a means of getting eggs in mass quantities.
I think all of the aliens contain the full amount of alien DNA, Queen and all, even in the regular adults.
The rest of the Queen's growth, what makes her develop into a Queen, and essential stops the regular adults from growing into Queens as well, may be as simple as something else is added to them during their egg development to ensure they become a normal adult.
Once in a while, perhaps randomly, or on purpose, the Queen will lay egg that have not been altered, and their phenotype it for another Queen.
When a regular alien makes an egg without the Queen being present, then the egg is guaranteed to be a Queen.
---------This idea actually loosely works with terrestrial ants and bees too. When the Queen dies the workers born to eggs layed after her death, will not be exposed to the Queen's royal jelly, and thus never sterilized, and will then lay eggs for unfertilized, Male bees or ants, so that the genes of that hive can continue by mating with newly hatched Queens-------
I know this is not exactly what I was explaining the Aliens to do, but it does parallel the single adults making Queen eggs idea.
This also means it would be very dumb to infiltrate a hive to just stop the infestation by killing the Queen. Maybe if she gets killed all the adults will scatter and all make new Queens elsewhere, next thing you know hives are popping up everywhere.
Kind of like going over the anthill with the lawnmower.