The general player base needs to improve

[RiyahArp]

The expert roulette already probably doesn't get used as much as level and 50/60 dungeons. If you increase the potential rewards with harder experts, that's incentive for players to optimize themselves through these....

You're not really getting my point. I don't know how much clearer I can make it.

If you want to make the players better, and things like rabanastre and shinryu have failed at that, you can't do things that are less difficult than it. Even if it's harder than current expert, you will still have the same problems. To really make players good, you have to make them either perfect the mechanic or die and be unable to complete the instance. But current casual content really doesn't demand this, and only ex primals and up demand it consistently. So the changes you will make will need the teeth of mechanic or die gameplay to teach the players what you want, in the same way Shinryu or Rab teaches you to look for a target outside of the arena and run the correct way or die (although surecast or fully mitigating the attack prevents it too in shin's case.) But they must be harder than those two, and that's perilously close to an easy EX trial or very easy savage. Otherwise it's just bardem's mettle, where it doesn't teach anything and you can carry people through it.

I don't think people care enough about rewards to do hard content. Arguably people stop caring to even do easy content; people stop doing the 8 man stories once they get a weapon for their main, and 50-60 roulette is dead because poetics and creation is worthless to any vet in the game. Carrots only go so far; people aren't going to do an hour of wiping for a few tomes. You'd need the stick; if you don't be hard expert, you can't progress the story.