Can Mr X insist that by a certain date (say 6 mths from now), he will draw a line. Whatever was found and handed in to him by that date will constitute the scheme’s library. Anything found by anyone after that date, even if it’s indisputably a true record, will not be considered in any decision making of the SC or OC.
A record is a record. Imagine how that cut-off would be greeted in a court of law? All he can really do is ask people to hunt out their various bits and bobs and he should suggest a reward, not threaten an unenforceable undertaking not accept records that they have forgotten about and no longer care about anyway.
As for payment, if he is asking for payment as a committee member, that’s not acceptable. If he is asking as an individual providing service to the scheme then he can’t participate in the relevant discussion.
Bad idea all round.