One of the great things about software development is that any reasonably bright human with the right training (or self-training, given available documentation) can do it. It doesn't require special equipment; your average PC and an Internet connection is quite enough.
(And it's gotten cheaper and easier. Back when I learned BASIC on the Commodore 64, that computer cost $1400 in today's dollars, plus another $700 for the floppy disk drive and $100 for a box of blank disks. Today, kids can learn to code on a Raspberry Pi that costs $35, plus $5 for an SD card; so it's cheaper by a factor of fifty-five ... and thousands of times more powerful.)
A consequence of this is that governments cannot prevent people from doing AI research in secret.
Would it help to require ethics classes for computer-science students? Maybe — but given the political climate, I would expect them to focus more on anti-piracy, pro-espionage, and telling students that they would be horrible, evil monsters if they wrote the next PGP, Tor, BitTorrent, or Bitcoin.
I don't see how your argument at all follows. Some software projects are impossible without large teams - or at least, impossible to do in any reasonable amount of time. And as the number of people who know a secret increases, it gets harder and harder to keep, not just because of increasing risk of deliberate betrayal, but because of increasing risk that someone will screw up on the procedures for keeping communications between the people involved a secret.
Here's a question: are there any policies that could be worth lobbying for to improve humanity's chances re: AI risk?
In the near term, it's possible that not much can be done. Human-level AI still seems a long ways off (and it probably is), making it both hard to craft effective policy on, and hard to convince people it's worth doing something about. The US government currently funds work on what it calls "AI" and "nanotechnology," but that mostly means stuff that might be realizable in the near-term, not human-level AI or molecular assemblers. Still, if anyone has ideas on what can be done in the near term, they'd be worth discussing.
Furthermore, I suspect that as human-level AI gets closer, there will be a lot the US government will be able to do to affect the outcome. For example, there's been talk of secret AI projects, but if the US gov got worried about those, I suspect they'd be hard to keep secret from a determined US gov, especially if you believe (as I do) that larger organizations will have a much better shot at building AI than smaller ones.
The lesson of Snowden's NSA revelations seems to be that, while in theory there are procedures humans can use to keep secrets, in practice humans are so bad at implementing those procedures that secrecy will fail against a determined attacker. Ironically, this applies both to the government and everyone the government has spied on. However, the ability of people outside the US gov to find out about hypothetical secret government AI projects seems less predictable, dependent on decisions of individual would-be leakers.
And it seems like, as long as the US government is aware of an AI project, there will be a lot it will be able to do to shut the project down if desired. For foreign projects, there will be the possibility of a Stuxnet-style attack, though the government might be reluctant to do that against a nuclear power like China or Russia (or would it?) However, I expect the US to lead the world in innovation for a long time to come, so I don't expect foreign AI projects to be much of an issue in the early stages of the game.
The real issue is US gov vs. private US groups working on AI. And there, given the current status quo for how these things work in the US, my guess is that if the government ever became convinced that an AI project was dangerous, they would find some way to shut it down citing "national security" and basically that would work. However, I can see big companies with an interest in AI lobbying the government to make that not happen. I can also see them deciding to pack their AI operations off to Europe or South Korea or something.
And on top of all this is simply the fact that, if it becomes convinced that AI is important, the US government has a lot of money to throw at AI research.
These are just some very hastily sketched thoughts, don't take them too seriously, and there's probably a lot more that can be said. I do strongly suspect, however, that people who are concerned about risks from AI ignore the government at our peril.