You are correct about key management being hard. I’ve been telling folks that absolutely insist on getting into Bitcoin that it’s best to leave out any notions of convenience at all, as convenience is the enemy of security. If you absolutely must have the stuff, stick to a cold wallet using pen and paper. It still has its own downsides, but it’s arguably one of the most simple ways to handle the keys problem.

Except that's irrelevant. Key management doesn't mitigate the threat against you.

If the person who kidnaps you believes you have the necessary keys on you, or remember them or whatever, they aren't going to let you go because you genuinely do not have the ability to provide them.

I fully agree with this sentiment. The burden of proof rests upon the kidnapped person to present the cryptocurrency or say it was “lost in a boating accident” but good luck proving a negative, in which case, you’re probably dead.

... and you don't even have the option of coughing up the keys to save your life.

you can just keep a small amount (~$100) on a hot wallet for daily spending, and keep the rest under a multisig scheme or something.