You are absolutely right when you say: "There is no legal, factual, or psychological justification for the current custody arrangement" That is because there is little scientific basis for child custody evaluations (see recent story on NPR). I am familiar with a Christopher Lane in the DC Metro area, who charged well over $10,000 for bunch of tests that had no scientific basis and then acted like he was a hired gun for one side of the case. It is a business and it should be recognized as that...and it is making money off of children's futures.That was a surprisingly good NPR segment. I will post the audio if anyone has trouble getting it from the NPR site. It said that court-ordered child custody evaluations should be abolished.
Some of those psychological tests do have some scientific basis as screening tools for various disorders like schizophrenia. But such screening is useful in less than 5% of custody cases. The rest of the time, the tests have no scientific basis for saying one parent is any better than other parent, or anything like that.
Yes, of course the child custody evaluator acted like a hired gun for one side. There is no other role for the evaluator, as far as I know. Mediators look for compromises that might be acceptable to both parties, but the child custody evaluator's job is just to generate evidence that might be used by one party in a custody trial.
I now have a court-appointed child custody evaluator, but it is not yet clear whether she is going to do the evaluation or not.