A bit late, but for your first point, what methods do you propose? The existing ones aren't good enough, with every merchant wanting to know as much as they can about you. In person of course cash works fine, and long ago I've mailed money orders, but neither is feasible for online. I'm glad PayPal exists and use it for some things, but of course PayPal knows all about me (I've even used their credit system before) and downstream merchants get bits of that + whatever else they require besides the money and a shipping address. (Like a phone number, though few ever try to verify them it's not an unreasonable step to try and cut down on buyer fraud. Seriously buyer fraud is huge, lots of dishonest people will buy something on ebay or wherever and then claim it never showed up, or the wrong item was received, or it was damaged, or.. all possibly perfectly normal issues that exist to help combat seller fraud, but the current tradeoff for disputes is so heavily stacked in favor of the buyer with the current systems that many times the seller can do nothing about a lying buyer except try not to deal with them again and/or require more information from the next person.)

Ultimately it boils down to, without comment on the desirability of making it possible to purchase illegal goods, can your proposals match the low amount of information darknet markets require along with the low amount of friction in making a payment? (A shipping address for physical items is the maximal information needed by any party in that whole system.)

For your second point, you can opt-in. Basic escrow has existed since the beginning with m-of-n signature transactions, various wallets have UIs for it. I'll just leave this here: https://en.bitcoin.it/wiki/Multisignature For "risk-absorbing systems" for merchants, those too have been around. BitPay is probably still the most popular, and it's several years old now. https://bitpay.com/ If you as a merchant use them, you can if you want not even bother dealing with BTC and its inherent risks at all but still accept it as a payment method.

For your third point I agree (elder)¹ fraud is a problem, and that if the scammers extract payment with a CC there's at least a chance of getting some money back... but that's not the only way they extract payment. Even if you made CCs magical anti-fraud devices, there would still be unacceptably high amounts of fraud targeting these types of people, because fraud is a complex problem and the institutions most capable of addressing it systematically would rather live with its predictable costs. As such I don't think adding BTC to the mix would harm things (or help things as a BTC fanatic might try and argue) by a noticeable amount in this area.

Admittedly I'm not too confident on this when applied to fraud more broadly; specifically I'm thinking of the new ransomware threat model people have had to contend with in the last few years. Overwhelmingly those attacks (not just against elders, but industrial infrastructure and so forth!) extract payment with cryptocurrencies, though sometimes they accept gift cards etc. Restricted to the elderly, more traditional computer related schemes like "coerce a phone call to a number for 'technical support' and get victim to grant remote access to their computer, 'discover' malware, have victim pay for 'fixing' it via CC/gift card/bank wire..." are still probably going to be the most common. And of course as I wrote above, by having a payment mechanism that shifts the tradeoff in fraud disputes back to the seller, we might see an increase in seller fraud, but how will that compare to the decrease in buyer fraud?

¹A not so elder relative got tricked out of $120 not too long ago, which for him is a significant chunk of change. Fraud is a multi-spectrum problem and in many respects only seems to be getting worse over time.