Just a thought:
Turning down the assignment because the appraiser already knows the price, doesn't sound good enough. If the appraiser accepts the assignment, the appraiser is going to receive a copy of the PA anyways.
Having the guts to do the assignment doesn't make ANY sense to me at all -- as in, at all.
This appraiser is related to one of the parties. That's about all it takes to raise the conflict of interest flag. This appraiser is not a disinterested party.
This appraiser is vulnerable to every conceivable charge. If something goes wrong, he won't have a leg to stand on with the state board or a tribunal. And that's after all parties, including the lender, have run him through the rack. The courts really understand conflict of interest.
Intelligence is learning from others. You don't have to experience everything yourself. Life is too short, and too precarious.