just a nice big city where there is an apartment block housing situation for the middle class, a shanty town for the poor, rich people have large grouped condos filled with expensive goods, some grand palace, a large open air market with surrounding shops, maybe a temple section, maybe a garden/park area, maybe an old school guild area with respective proper guilds (mages, thieves and whatever iteration the warriors guild is), possibly a sprawling sewer area for enemy encounters, and last but not least, a crapton of NPC's to fill out the city, maybe double or more the solitude NPC's (with closed off city sections so running such a thing wouldnt overload consoles/ weaker PC's), be it a revisit to the Imperial city, a visit to blacklight or a city in high rock/hammerfell
obviously beth probably has the final DLC(s) planned, but this would be my one wish and what I would add to the game if I just had to pick one thing