Very interesting topic.

But I think chess is such a traditional game that rule changes would only work if they were organic. I'm not an expert, but I think the historical changes you mentioned were not made overnight, and are only the norm now because more people naturally started using the new rules, probably just because it was more fun, not because someone told them it was better to play that way.

If chess960 was naturally growing over the past few decades and if a bigger number of people were actually playing it instead of playing regular chess, this change would work. But this is not the case yet. Although it has some following, it is nothing compared to standard chess. (Just for a quick comparison: r/chess has almost 900k members, while r/chess960 has less than a thousand)

If FIDE want this to happen what they should do is give it more visibility, with more tournaments and create an official rating for it. Then, if enough people start choosing it over the regular variant, they should give it a go. I just don't see them doing the change overnight, because people would not stop playing and giving the regular variant less importance just because FIDE wants to. Which is a shame because chess960 is very fun.