To copy-paste my previous comment:

I don't really mind a pity system being implemented in the game as its current sparking system is absolutely awful, requiring you to pull the same exact SSR 15 times to get enough currency to buy the SSR you want, nevermind how crazy it is to get just one.

With a reliable pity system, at least you get something if you pull enough, even if it's not the SSR you want. However, my only real concern about such a system is that getting an SSR might not be so special anymore if enough people get the same exact ones, and their value might actually tank as a result.

Not only that, later content might revolve around specific SSRs so much that it might become impossible to clear without them. This hasn't been the case so far, although the most recent Lostbelt in JP has become more insanely difficult than all the others before it, to the point people complained how impossible it was even with meta SSRs when it first came out.

Maybe they can implement a hypothetical pity system in such a way that not everyone will have the same exact SSRs, thus increasing the odds of players getting at least one SSR while still making them valuable.

However, with the way FGO is raking in money right now, I don't see them implementing a pity system in the near future. They might consider that if their revenue plummets to the ground, but I honestly don't know.