With the expansion fast approaching, there's a lot of people that have an opinion on what Yoshida should do about gaining entry into the new content. This is how I think would best suit Final Fantasy XIV.
When 2.1 - 2.55 main scenario quests were released, they were filled with quite a bunch of pointless quests. I know many players at the time did not care about these too much since it had been 3 months since they last did any MSQ. However for anyone new to the game from then on, it does become quite a chore to go through them all.
I think the best thing to do is focus on this part of the game before 4.0. The level 1-50 quests are somewhat fine for now since you are using these quests to level. The 1-50 quests might need a look into before 5.0 hits, but for 4.0 the 2.1 - 2.55 MSQ is a much bigger hurdle for new players I think. It does kind of suck that after the amazing climax of Ultima Weapon that you're doing some boring and useless quests. I really hope someone can sit down and look into them so that they become streamlined.
Apart from that, I really don't like the idea of a leveling potion or letting people to skip the story to catch up. The way Final Fantasy XIV is designed, it doesn't matter how new you are, you still get an almost identical experience as someone who first purchased the game a few years back. The only difference is that lower level areas are less populated. But with level sync and roulettes, people who pick up the game in 2020 will have the same experience during Sastasha as people right now.
Also the story in Final Fantasy XIV is continuous. What happens in 2.X is related to what happens in 4.X and so on. Other games have separate stories for different areas, so it doesn't matter if you start in an expansion area or not. But in XIV it all flows from 1 quest to the next. You let people skip the story and levels, you'll have them miss out on hundreds of hours of well designed content which ultimately makes the game smaller for new people.
Also finally I want to say that Heavensward has done an amazing job at fixing a lot of A Realm Reborn issues with regards to MSQ. The actual story has extremely limited useless quests (Just those dreaded moogles) and post 60 quests are just streamlined with good story. There are amazing solo battles like the Grand Melee and 3.4 MSQ story battle that also keep things interesting and fun as you go though them. If new people had to go through this kind of content to get to 3.0, there really wouldn't have been much complaints I think because of how amazing it was done. The search for Ga-Bu in 3.4 was the absolute max amount of useless content in MSQ that should be allowed though.
People will complain about needing to do the Main Story to reach the expansion, but if you give them good content to go through to reach the expansion, they will quickly forget about their complaints. 3.X MSQ is a clear example of good content that people can enjoy to reach an expansion and I hope 2.1 - 2.55 MSQ can be changed to be more like it.