They could pull a FFXIV and have the players help rebuild the city in exchange for experience and rewards. For context, one of the regions had their city partially destroyed, so the developers held an event which spanned multiple months rewarding crafting/gathering professions additional experience and event-specific items for donating items to select NPC's. Each tier of reconstruction saw new buildings being added, and eventually the entire ward was rebuilt and converted into a new zone for player housing.
They could theoretically do the same for The Undercity for equality purposes.