Onana wasn't dodgy, he was hyped and played a great CL season for Inter. Hype drives up prices, dodgy doesn't fit here in my opinion.
Antony wasn't dodgy as well - it was downright dumb. Ajax didn't want to sell late in the window, so they created a pricetag they thought would push away any potential buyers. We were just so dumb and desperate that we still followed through. I'd love to be in that Ajax office watching the reactions when the email came in that United were ready to pay that amount for Antony. I am sure they thought to be part of some sort of practical joke.
Otherwise, I do like the idea of such a comittee, although I also agree, it is probably difficult to execute. Could consist of anonymous questionaires though - like if a deal seems dodgy for the FA, then it triggers a process where every CEO of the league clubs has to answer what they think would be a fair value of the player. Then FA takes the averages and if the deal in question is in excess of that by more than 10 or 20%, it is either stopped, or a more thorough process has to follow.