Currently, players are capped at obtaining 300 Allagan Tomestones of Mythology per week. The rationale behind capping any kind of end-game currency is to ensure a smooth transition of players into end-game and provide some delay such that players have a continuing reason to play for many weeks. No doubt, in the future, there will be new similar currencies introduced, so addressing the following issue earlier rather than later would be preferable.
This deficit is inherently bad because it fragments players who would otherwise be playing together. It makes it impossible for players to catch up and join their friends, especially if they make new friends who are further in. It also makes it impossible for advanced players to establish friendships with newer players and bring them up to speed. As cooperation and collaboration are cornerstones of a PvE-centric game like FFXIV, the core game philosophy should be designed around supporting these goals.
Problem: Although the rationale itself is sound, the current implementation of a weekly limit creates a permanent deficit between players. A player who begins collecting tomestomes a week later or a player who is unable to play for a week will never make up that lost week's worth of stones. This creates a gear-gap that, so long as new gear being acquired, can never close.
Solution: Rather than a weekly limit, tomestones should have a lifetime limit that increases weekly. For example, on week 1 everyone can only obtain 300 tomestones of mythology. On week 2, everyone can now obtain 600 total, including the ones acquired in week 1. This allows players to catch up when they begin collecting at a later date or miss a collection period.
The result is the same controlled progress gate: The developers retain control over the rate at which the lifetime cap increases so they can ensure players do not obtain too much gear ahead of schedule. This can then be achieved without fragmenting players into those that have obtained the cap each period and those that have not.