Good questions.

What sorts of scenarios involving the emergence of AGI do you think regulating the availability of LLM weights and training data (or of more closely regulating AI training, research, and development within the “closed source” shops like OpenAI) would help us avoid?

Honestly, we might be too late anyway for avoidance, but it's specifically research of the alignment problem that I think regulation could help with, and since they're still self regulation and free to do what OpenAI did with their department for that...it's akin to someone manufacturing a new chemical and not bothering any research on side effects, only what they can gain from it. Oh shit, never mind, that's standard operating procedure isn't it, at least as long as the government isn't around to stop it.

And how does that threat compare to impending damage from climate change if we don’t reduce energy consumption + reliance on fossil fuels?

Another topic that I personally think we're doomed to ignore until things get so bad they affect more than poor people and countries. How does it compare? Climate change and the probable directions it takes the planet are much more of a certainty than the unknown of if AGI is possible and what effects AGI could have. Interesting that we're taking the same approaches though, even if it's more obvious a problem. Plus profiting via greenwashing rather than a concentrated effort to do effective things to mitigate what we could.