This isn't a specific recommendation, but perhaps worth considering among other choices for the portion of the problem which is portfolio and withdrawal management.
What can be done to make it so no financial decisions are needed?

When the person in question fails the cognitive test, liquidate the portfolio they intended to live from. Buy one or more annuities with the proceeds.
No further financial decisions to make, no financial planner needed, you just get money in your account every month till you die.

More often than not, cognitive decline becomes a serious problem at a somewhat advanced age.
Annuities are not good "investments" in terms of return on your money, but they do serve a purpose.
The key observation here is that they generally have quite high payouts when purchased at an advanced age, since at that point the insurer's calculation is primarily about life expectancy, not time value of money.

For those who want to leave an estate, just handle that part of the portfolio separately.
Perhaps a portfolio aimed at long run wealth preservation rather than income, like a bunch of long term holds that are never touched.


Another random thought: The charms of TIPS ladders are generally underappreciated.
A lot of people think of them they way they think of bonds, but they are as different from normal bonds as bonds are from equities.
There is perhaps a case to be made that they are a good fit for at least a portion of most retirement portfolios.
And of course, in this context, they represent a portfolio and income strategy with no further investment decisions or actions required.
They don't address longevity risk.

Jim