Each epic FATE provides some token for special turn-ins (like Chi Bolts or Formidable Cogs), and in Shadowbringers and Endwalker content, rewards also include bicolor gemstones, the amount depending on your contribution.

Now, after getting the turn-in rewards for each epic FATE's token (like the Level Checker mount for Chi Bolts), there isn't much reason to keep these tokens in your inventory after subsequent completions (aside from getting duplicates of equippable items, when applicable).

For my suggestion, I'd like to see an option for players to exchange tokens from Shadowbringers and Endwalker epic FATEs for bicolor gemstones. A 1:1 ratio would work, though it could be nice for a 1:2 or even 1:3 turn in of special tokens for bicolor gemstones.

Theoretically, such an exchange could apply for epic FATE tokens from ARR, Heavensward, and Stormblood, though it might require a special NPC specifically for a token to bicolor gemstone turn-in instead, as shared FATEs and the gemstones aren't really a relevant system until Shadowbringers areas.