Prepared it all? I am not no sure. He seems genuinely angry and shocked when you talk to him. Plus, he was incredibly easy to kill. I mean, dispatch a few weak Securitrons, Science! your way past his terminal (or find one of the keycards just lying around) et voila, the Master of New Vegas is within your grasp. No override on the elevator, no backup security systems, no blast door or something. You would think someone with such a sense of preparation would make sure he was secured. At least make him harder to get to if you betray him at the Fort, I mean, he states he knows you are coming and hunts you, no?
Yeah, a liberated New Vegas will be in a gloomy state. But even Shady Sand started with a bad history, eh? Sure, the only protector of the region is army of robot, but they're not a mere protectron. You'll also have Boomers, Three Families, Kings and maybe Marcus's Jacobstown as your back-up too.
Boomers just want to blow shit up (if somebody makes a better offer I could easily see them turn against you), the Three Families care only for themselves (and the Omertas were ready to attack the Strip for the Legion), the Kings only protect Freeside, and why would Marcus come to the rescue of New Vegas?
Also, Shady Sands based itself on more than goddamn Casinos
Source of income depleted? That's why you'll have to protect the President, so when times come, blame will be on him and his general, not New Vegas. People will keep coming to the casino.
The general you ordered thrown down Hoover Dam? And if conflict arises (and it always does, even with the upgraded Securitron Army), New Vegas will be less attractive. Plus, you committed an act of war against NCR; they will certainly no longer protect the roads leading to the city That's another thing to consider, because the people who have to income to invest in New Vegas live very far from it. And House himself says the garrisoned NCR soldiers form a major part of his income. Not any more.
How about the chaos? Just deal with them right from the start. You don't need to rely on House, NCR, and Legion to wipe out Fiend, Powder Ganger and Khan. Do the quest in right method, and they're as good as gone.
The chaos doesn't come (only) from them. Freeside, Westside to a lesser extent, Northside, squatters, NCR citizens rebelling, all are hotbeds of violence (save maybe for Westside who polices itself nicely).
Best ending my ball sack.
I would have liked a Courier with high Science or Intelligence or seeking help from the Followers to say ''Oh no you don't -Activate Failsafe-''. Bingo, one obedient AI. You would have to actively seek that before, no quest and no markers. Would have been very satisfying. But again, you can't please everybody.