I'd like to see a more direct, and malignant, link between the two social groups in the city. One that anyone could observe. Perhaps businesses take advantage of the poor by employing them in aweful and dangerous working conditions for measly pay. Such as employing children to maintain and repair a svirfneblin sized factory with plenty of grinding, crushing machines. Or force newly arrived refugees with no means into years of indentured servitude on a farm? Perhaps some of the quests could have a few unfortunate citizens to save from the perils of a brewery that employs seedy hobgoblin guards rather than pay protection money to the Tigereyes?
I'd like to see more concrete and obvious reasons for citizens of Lower to feel abused and debased by citizens from Upper. I would imagine certain elements of this exist in game, though I haven't come across them.