OP is proposing new incentives to take ranked PvP more seriously to the new audience FFXIV PvP is getting. PvP in FFXIV has been unpopular for a long time and the Feast was a niche gamemode which was ridden with botting, boosting, win-trading and other such sorts of cheating. Players were uninterested in PvP and Feast in general let alone grinding for top 100 and the fact that Feast is entirely gone from the game now is a testament to that. However we're now seeing a huge increase in interest in PvP because of Crystalline Conflict (CC) and the rework of every job in PvP. Considering the nature of FFXIV and the way it keeps old content from as far back as ARR relevant in a variety of ways, its only appropriate that PvP related content is designed the same way.

Very few things are time-gated in this game and thats one of the best things about it considering the rest of the gaming landscape nowadays. I would argue that old Feast top 100 players should have their unique titles that separate them from the new PvP players but the rest of the rewards should always remain obtainable in a pool of ever expanding rewards for higher level players to choose from. FOMO is a terrible practice in modern gaming and I'd say that this game is a sort of safe haven from that. Such an addition would only expand on the game's low-pressure direction and on the PvP modes in general. All of those items should be made accessible once more in some shape or form even if its not necessarily the way OP proposes it.