Lot of factors and variables in considering a Gordon sale.
Objectively my stance has nothing to do with needing more proven commodities for this season. We need a secondary goal threat to assure some level of safety, but Gordon's inclusion or exclusion I don't find makes our breaks or league position. Especially considering a fair amount of depth at his position that are arguably on his level currently. Once you factor a Chelsea return being reinvested, its hard to think broadly speaking we wouldn't be able to improve.
Broadly I dont really care where we end up in the table really for the next 2 maybe 3 years if we are consistently not in a relegation scrap, as long as we are on a developmental track that is maturing talent and selling for profit to eventually close the gap (far as I see it don't see another viable model). Gordon fits the youth movement, but he also right now is seemingly also fitting the selling for a high profit part of that equation. One can be engaged by his potential and also see his sale as the viable basis for acquiring more players of similar intrigue and eventual opportunities. Brighton sold Ben White for 50 million, used 18 million of those sums on Cucurella, only a year later sell him for 63 million. Such a logic and model should be replicated and to the extent that Gordon is the leverage to reinvest (when there aren't that many other pathways of sellable players to generate funds rostered) is pragmatic.
If concerns are raised by Thelwell's ability to find the value propositions Gordon's sale would offer, I think that has some merit. If AG goes and he turns to Gibbs White for 30+ of that 40 that would cast the initial deal in a different light completely. That said deals like Onana do provide a basis and conceptually its the right order of operations. The club has to get comfortable at selling players with intention and thinking of it as an opportunity. Hard as it is to say I do think the sell would be wise.