The outermost layer should concern issues people you are trying to influence care about. Alas, aside from global warming, this means ignoring things that won't happen in the next 50 years. The outermost layer should also take into account confirmation bias so don't claim in this layer that the possibility of developing a super-intelligence reduces the optimal amount of money we should spend today on slowing global warming because this will cause much of the elite media to reduce their opinion of you. The outermost layer should also completely exclude anything that will trigger disgust reactions in the elite media even if this disgust is totally irrational. Finally, your goal in this layer should be to embed an elevator pitch that overcomes the absurdity heuristic you must encounter when you claim your goal is to develop a super-intelligence.

Although this speaks very poorly for our species, the danger of discussing existential risk in the outermost layer is that it will cause most people to find you uninteresting.

This appears to be a reinvention of milk before meat, one of those bad ideas that just keeps coming back. This sometimes works out not so well; people do understand the concept of bait and switch quite readily.

Basically, if you have bits that you know perfectly well look weird or stupid, then pretending you don't just looks fraudulent.

In my experience, in communicating on these matters to the public or generalists, it's definitely good to highlight benefits as well as risks - and that style of onion strategy sounds about right and is roughly the type of approach I take (unless in public/general discussion I'm e.g. specifically asked to comment on a particular risk concern).

In speaking to public and policymakers here (outer layer 1 to layer 1.5, if you will), I've found a "responsible innovation" type framing to be effective. I'm pro-progress, the world has a lot of problems that advances in technology will need to play a role in solving, and some of the benefits of synthetic biology, artificial intelligence etc will be wonderful. However, we can make progress most confidently if the scientific community (along with other key players) devotes some resources towards identifying, evaluating, and if necessary taking proactive steps to prevent the occurrence of extreme negative scenarios. In such presentations/discussions, I present CSER and FHI as aiming to lead and coordinate such work. I sometimes make the analogy to an insurance policy: we hope that the risks we work on would never come to pass, but if the risk is plausible and the impact would be big enough, then we can only progress with confidence if we take steps ahead of time to protect our interests. This seems to be effective particularly with UK policymakers and industry folk - I can have risk concerns received better if I signal that I'm pro-progress, not irrationally risk-averse or fear-mongering, and can hint at a reasonably sophisticated understanding of what these technologies entail and what benefits they can be expected to bring.

I would add a small caution on "astronomical stakes". It works very well in some rhetoric-friendly public speaking/writing settings (and I've used it), but for certain individuals and audiences it can produce a bit of a knee-jerk negative reaction as being a grandiose, slightly self-important perspective (perhaps this applies more in Europe than in the US though, where the level of public rhetoric is a notch or two lower).

The outermost layer of the communication onion would ... focus on benefits ... A second layer for a specialist audience could include a more detailed elaboration of the risks.

Since the specialist audience also reads the general-public materials this would open you to accusations of being two-faced (or even hypocrisy).

I am also not clear on the specific goals of this exercise. Do you aim to manipulate the public opinion (that's a craft with its own set of skills and many tricks of the trade)?

I don't think it's wise to make the outer layer "focus on benefits rather than risks." That sort of spin control will probably be detected and lower your credibility in the eyes of the public. But more importantly, panic isn't always a bad thing. (I'm assuming we're using "panic" broadly here: I don't remember any riots over IVF.) I'd like to see a little more panic about AGI.

Your concrete suggestions look good. For example astronomical stakes rather than existential risk is a good move, because it's balanced. And it's not a good idea to push too hard on doom and gloom: that will lower your credibility just as much as positive spin. The outer layer doesn't need to be positive, just suitably non-technical and representative of the overall layout of the issues.

This is an interesting consideration. One related thing I think about is that potential technical contributors will usually need to pass through the outermost layer of the onion before they get to the inner ones, and so not bouncing them off with something that seems too non-technical is important. This should be adjustable independently of the "alarm level" of the language, though.

To paraphrase "Why Flip a Coin: The Art and Science of Good Decisions", by H. W. Lewis

Good decisions are made when the person making the decision shares in both the benefits and the consequences of that decision. Shield a person from either, and you shift the decision making process.

However, we know there are various cognitive biases which makes people's estimates of evidence depend upon the order in which the evidence is presented. If we want to inform people, rather than manipulate them, then we should present them information in the order that will minimise the impact of such biases, even if doing so isn't the tactic most likely to manipulate them into agreeing with the conclusion that we ourselves have come to.