It doesn't seem particularly difficult. A discerning judge, a caring social worker, and an honest doctor with adequate time to consider the issue carefully should have little problem seeing the right course of action.

It only becomes difficult when you also have to fight against the incentives.

When the 'guardian' gets to bill the estate when their doctor friend writes something down, and the judges are listening to the letter of the law as argued by the expert lawyers rather than the flabbergasted victims, then it's a hard problem.