Fourth, I gave a warning to a relative who told me that a friend would manage her BTC issues. I think there is nothing to add. However, for the folks reading this, do not transmit any access to anyone you can't 100% trust. Now figure out how many people in life you 100% trust.
Some people might seem 100% trustable at time A, but then death/incapacitation happens at time B.. so then such previously trusted person is put in a position to "do the right thing," yet such person knows enough to know that no one else knows, so is such person going to do the right thing, or not? Maybe the person does not even know, until put in such circumstances of considerable amounts of possible life-changing wealth, and no one else will know. Some of us might believe ourselves to be capable or not capable of doing the "right thing," and there will also be times in which "the right thing" will be subject to interpretation...and think of another possibility, the "right" thing (could well be interpreted to be divisible.. .hahahahahahaha..
by 100 million.... or even time-delayed preserving of a "back door" that may or may not be the "right thing" to do).
I agree and there is one more big problem about giving other trustworthy people access to your bitcoin: what if you do indeed get hacked, how would the person that you granted access to your coins prove that it wasn't them who moved the coins off your wallet? That is a very uncomfortable situation if you think about it. You trust someone 100% and you are ok with that person holding your keys, and out of a sudden the coins get moved and that person is not responsible.
There are very good reasons to find other solutions to handle private keys safely and next to avoiding theft, one good reason is to avoid misunderstandings like the one I explained above. I think almost any trust relationship would somehow suffer from such an incident as nobody can prove with certainty what really happened unless a scammer would make a mistake.
And as you mentioned, trust is fragile and has so many components that can change a certain relationship for better or worse sometimes in no time, and sometimes over a longer period of time. Bitcoin is highly sensitive to these things. If someone trustworthy moved currency from a bank account without your consent, the whole problem would most likely be attributable to whomever moved the funds. There is hardly room for misunderstandings like there is when bitcoin wallets are used.