Currently, it would be nice to be able to select the same leves as your party members. This is not easy to achieve and is largely off putting. Surely, some small adjustments to the system could make them more popular if they would separate the allowances for battle and crafting/gathering leves as well.

Levelsyncing that allows high-level players to party up with low-level players to do this content regularly would be good also.

New additional expert battlecraft leves that require you to act cautiously and swiftly in battle just like the masked carnival would be awesome.

Maybe only certain leves become available at specific times/condition (weather).

Open world content that makes the world entertaining and different.