Thinking about future changes to the qualification system, or how to avoid the Petrounias situation. Other than holding another qualification competition later in the year, if the FIG didn’t want to organise and pay for that, they could:
A) Grant a qualification place to any medallist at the last year’s Worlds/Olympics if not otherwise qualified. This would only apply to Petrounias this year. If you expand to event finalists for example Filipa Martins would get in for uneven bars at Worlds as well. This rule would only help a very small number of the very best gymnasts, but that’s who would be missed most at Worlds.
B) Give the specialists another opportunity to qualify at the continental championships. If you needed a medal to qualify this would only add a handful of people, but the disparity between the continents would make this a very variable standard - Africa MAG and Oceania would dominate the extra entries, and most years there probably wouldn’t be a Petrounias level competitor to balance it out. This also wouldn’t help anyone who was injured for both World Cups and continental championships.
Interestingly, AA competitors already have two opportunities to qualify. I don’t think anyone tried this year, but the rules explicitly state if you qualify on all the apparatus (via the World Cups) your AA score will count at Worlds. Anyone trying this would need two vaults, and it’s probably only really possible for women, but I wonder if someone will try next year, with the added importance of getting to Worlds to qualify for the Olympics.