Not super possible. People that have played against the deck will know the deck. Trying to make it so that it's harder to discern this information is a fool's errand, if you ask me.
The argument that persuaded me that banning scouting was bad was that otherwise, the people with the most friends at any given tournament get an advantage. It's not enforceable to stop players from sharing their in-match experiences, and by the end of the day, a competitive group of friends would probably roughly know every player in the cut's archetypes and/or weird splashes, if nothing else. This is only the same information you could get by just watching a game, no more, no less.
I don't think there will ever be any deck that's so super secret that if the decklist was never released to the public it could never be replicated; a good player who has played against a deck could almost certainly replicate it if they wanted to. Even if not card for card, I'd imagine pretty damn close.
In a high level tournament, they should collect decklists and perform more than 0 deck-checks throughout the day (probably in the top cut), I think. Leaving this out means people can get away with illegal decks.