Spaihts's David has been reborn from the ashes of Lindelof's more nuanced character. We our just one dastardly master plan reveal, while quoting a line from Milton's Paradise lost, from having a full blown Bond villain on our hands.
Not to come off too pop phycologist, but David's effectively a psychopath. He's developing human emotions, but he doesn't have any empathy to underpin them. It's like giving Hannibal Lecter a bioweapon to play with; he's going to be more interested in it's effects than the consequences of those effects.
I don't believe David's decision to bomb Paradise is out of revenge; it's just a scientific experiment to see the black goo's effects on a planetary scale. If a few thousand Engineers have to die along the way, then so be it. Eggs and omelettes.
Talking of psychopaths and God complex, reminds me of Hannibal Lecter's line in Manhunter:
'If one does what God does enough times, one will become as God is.'
This is David's metamorphosis from subservient android to deity. The black goo now gives him the power to create and destroy on a planetary scale, ergo, in his mind, he's now a God and humans and Engineers are imperfect by comparison.
As for the alien, I agree with what a couple of other posters have mentioned on here over the last few weeks. That David is trying to create creatures in his own idealized image of himself. A being unclouded by conscience, remorse, or delusions of morality; a Perfect organism to live along side him in his planned utopia; washing away the imperfections of the Engineers and humanity in the process of their creation. In some respects it's a cool idea, just have to see how well it's executed in the film, because if done poorly, it runs the real risk of coming off all Machiavellian.
Thinking about it some more, I feel SpeedyMaxx is right and despite what some who saw the footage at CinemaCon are claiming, I now think it is the Engineers being bombed by David and not another intermediate race of humanoids. The size of them as David walks between their corpses in the plaza, the shot in the red band trailer of one of them being dissected, looks like Engineers to me. Plus, as Hick's reminded us, they were referred to as Deadgineers on set.
Still have strong doubts though, that Paradise is the Engineers home world. One city, no other nations, no government or military; doesn't seem much like a home world to me. So I still feel there's a possibility Engineers will be reintroduced in the next film, or certainly in time to become the Space Jockey on LV-426, if RS goes down that route and shows it happening rather than implying it through other events.