I just successfully tested changing music by region, and changing it between continents on the world map after getting on/off the airship. I had to override the default audio transitions with eventing to make it change smoothly but it worked.
I've reconsidered having a subclass system for my first two games since there will already be plenty of variation in playable actors and usable items in the games. The third game will need it because of the basis for the story but I want the actors in the first two to be more focused in their roles.
I performed a test of changing an event's sprite based on who is in slot X of the party. Conditional branches have made it successful. This helps for cutscenes that bring out the whole party correctly onto scene even when members are changeable.
Planning out my second game a bit with my first game because they will be in the same world. My development time might be much shorter for the second game as a result. I'm hoping to finish them both next year.