In the past Naoki Yoshida has repeatedly stated that he's perfectly fine with players taking extended breaks from FF14, and up until the introduction of the "PvP Series" Battle Pass with patch 6.1 this has been supported by the complete absence of game mechanics designed to induce "fear of missing out". While there has been automated demolition of player-owned plots (houses) that mechanic has "only" demanded players to maintain their subscription and putting in a token effort of logging in every few weeks to avoid losing their in-game property.
Now the developers can't just backpedal on this and claim that they did a lil' fucky wucky, so the solution to this that I propose is to make each Series cumulative.
That means that, when Series 2 releases, 1 stays open for everyone who hasn't finished it already. When Series 3 releases, 1 & 2 stay open to everyone who hasn't finished them already, and so on. This way the game has something that encourages PvP fans to keep playing, which is what I assume is the point of the PvP series, because they'll always be on top of the grind and they will be the first to obtain the series pass cosmetic rewards. But people who want to take occasional longer breaks, or players who join the game at a later point in time, are not punished for not forcing themselves to burn out on FF14 by grinding a gamemode they might not even enjoy all that much, because they don't want to miss out on the series rewards - or worse, for not having been there today when they buy the game in 2 years from now.