I was thinking later down the line for PSO2 after the Devs finish with the episode instalments, it could be fun to see a return of Eternal Tower from PSØ or something in the fashion of it. Maybe I'm speaking for myself but I thought that was a great addition. Or maybe even old zones.
I re-call gaming through areas like Dark Shrine / Arca Plant, thinking wow SEGA has some masterful level designers.
I'd personally love to see more areas like that find its way into the game if there is any future expansion content later on.