Ya know, in some really funny way, the One Piece treasure having nearly 3 decades of build-up behind it means it will most certainly disappoint in its reveal if it is anything other than a tremendously stupid Oda-tier gag like it being a pair of panties. A silly joke as old as the series coming to fruition.
Without a doubt, it would have the most memorable staying power if it was something that low-brow.
"I read this fucking shit for half my fucking life and it turned out to be some skimpy bikini? Fuck you Oda."