At the beginning the player would be asked "What is your past?" and is presented with the option to select previously completed expansions or nothing. Depending on the choice, extra dialogues and cutscenes could be added at different moments in the story to connect to previous content as needed. As an example on the lead up to a dungeon a player with past experience would have the normal sequence of events while a new player might see an additional cutscene introducing relevant characters, like trust NPC's, first.

Mechanically I'd like to see far less stat scaling between levels. The goal would be to remove levels as a hard requirement for content so that players of different levels could meaningfully interact. New skills could still be unlocked via leveling so that max level retains an advantage but the gap between min and max would no longer be a thousand or more percent increase. Instead the gap would be akin to the one between an optimal max level rotation and a max level character using only their basic skills or combos. With this system in place non linear progression through the story becomes easier to implement since a character would be able to meet the requirements for most content even at base level. New players would see a variety of content much faster as a result while more experienced players wouldn't have to worry about trivializing content if partying with low level players.