
"I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones!"
~ Albert Einstein
Not really a theory about the Engineers, but more of an idea that I had that and liked so I'll share.
What if The Engineers became extremely advanced, but had some sort of conflict on their world (the one Alien Covenant takes place on)
Somewhere along the lines a nuclear type attack happened and wiped out the entire adult population, leaving behind some younger Engineers.
These Engineers, being too young to have learned the full ways of the adult Engineer world, are left on the planet with all of the advanced technology, but are not capable of fully understanding what any of it means. They would need to evolve for however long, to reach the intelligence level that once was normal to their race.
Think of on Earth, all the adults die off in a global nuclear war leaving only younger generations behind to procreate and survive.
These Engineers are able to remember the elder generations coming and going via ships, which is why in AC when David bombs them....they all gather like children, or inferior beings expecting the "grown-ups" to arrive.
After ruining their world, some of the advanced Engineers who survived (the ones who died in Prometheus) set out for Earth to wipe it clean and start over, having no remorse for destroying the human race that had been created by their rival Engineers, but we all know how that played out.
Now David is programmed (unknown to him) to have his data and findings sent back to Earth were Weyland-Yutani have all the access to them after gaining clearance following Peter Weyland's death. He is allowed to continue his "experiments" with crews sent out to his general area for fake missions (obviously unknown to them), only to be used as guinea pigs for him. They let this continue until they feel he has created a perfect weapon for them to bring back to Earth.
Just a little something I came up with, if it sound interesting to you guys, awesome. If not then I'm not gonna sweat it, just a little entertainment.

Those are interesting points and I have thought of some of those ideas too. I also am probably not the first to make a connection between the David Bombing and Hiroshima and Nagasaki in a way.

Ridley says he wants "war of the world's" to be his next angle for AlienAwakening. Who knows about their homeworld, maybe something is in the new companion novel. Love Prometheus but I think Covenant may have usurped whatever intrigue was left

It is not far fetched at all. We have evil companies right now that would probably love this to happen. Picture the future of the Military industrial complex. Grumond-TRW or Boing-Monsanto out in space in a thousand years from now. We dont even know what they are up to now much less in the future.