For society to be sure of what code you're running, they need to enforce transparency that ultimately extends to the physical, hardware level. Even if there are laws, to enforce them I need to know you haven't secretly built custom hardware that would give you an illegal advantage, which falsely reports that it's running something else and legal. In the limit of a nano-technology-based, AGI scenario, this means verifying the actual configurations of atoms of all matter everyone controls.

A singleton isn't required, but it seems like the only stable solution.

Nothing short of a very powerful singleton could stop competing, intelligent, computation-based agents from using all available computation resources. If the most efficient way to use them is to parallelize many small instances, then that's what they'll do. How do you stop people from running whatever code they please?

Human brains are relatively unique in their size.

But all other human organs are not unique. Once you can successfully revive other animals that are like humans except for their brains, you can move on to humans for the missing parts. It makes sense to minimize the amount of dangerous testing on actual humans.

On the other hand, if the idea is to focus preservation on the brain only, then revival would be very far beyond our present abilities and we can't do meaningful tests even on humans today.

Horrible PR, even if you are doing humane (non-revival) experiments.

Surely the PR from failed tests on actual humans would be even worse.

happiness is what happens when things are going well, depression is what happens when things aren't, and the two moods must serve some sort of evolutionary function, right?

Depression causes inactivity, helplessness, not dealing with problems, cutting social ties, and sometimes suicidal behavior. It's hard to see how any of that could be evolutionarily beneficial in any scenario. (Which is not to say it's not an evolved behavior due to some different mechanism, like being tied to otherwise beneficial genes.)

Indeed, Wikipedia says the coccyx is far from useless in humans:

it is an important attachment for various muscles, tendons and ligaments—which makes it necessary for physicians and patients to pay special attention to these attachments when considering surgical removal of the coccyx.[2] Additionally, it is also a part of the weight-bearing tripod structure which acts as a support for a sitting person. When a person sits leaning forward, the ischial tuberosities and inferior rami of the ischium take most of the weight, but as the sitting person leans backward, more weight is transferred to the coccyx.[2]

If rules were relaxed or costs were lower somewhere else, then wouldn't for-profit drug development move there as well? Whatever the funding model, the actual research and laws that govern it are the same.

I fear somebody is going to complain that disruptive behavior is what we need to teach children so they can innovate and question authority. Open to discussion, but if it worked that way, we'd be overwhelmed with innovators and independent thinkers today.

Uh... We are overwhelmed with innovators and thinkers. This is the most innovative age in technology, science and the arts in history!

I don't know if childhood "disruptive behavior" is correlated or anti-correlated or independent of innovation in adulthood. But your argument doesn't seem to work.

Education is legally mandatory and if you don't go to a normal school you have to have some alternate acceptable form of education (e.g. homeschooling).

Worse than that, homeschooling is almost entirely exclusive to the Anglosphere. It is illegal in almost all other countries.

if you ask them to do any planning, for instance, they'll come up with designs that sound good but fail: they parrot back other people's plans with minimal modifications

Guessing the teacher's password describes a common human behavior. An AI that behaves the same way not just passes the Turing test, it might really be said to be as intelligent as a relatively stupid human.

Also, there's a huge quantitative difference between a student repeating what the teacher said, and an AI repeating at will everything written in all digitized books and Internet sites it has read. An AI that is a little less intelligent than a human in some areas will still be vastly more intelligent than any human in most other areas. Even if humans remain much better at certain tasks, it may not truly matter.

The biggest biological danger of casual sex was (to women) unwanted pregnancy. It's now almost gone thanks to modern contraception.

STDs certainly exist, but they too have become rarer. Syphilis used to cause a lot of mortality and disability, and was mostly (not entirely) defeated by antibiotics. And with modern health care and social safety nets, if you do get sick, your outlook is much better than even a century ago.