Since we have three weeks until gameplay release, I would sum up my wishes as:
0) General design philosophy being less lopsided towards "every mechanic reminds you it is board game", with
more simulationist - immersive "this is organic living world" vibe.
1)
Combat-army system different from civ6 1UPT
and old 4X stacking - you have interesting battles and AI often threatens you offensively, yet there is as little micromanagement as possible.
2)
Interesting endgame, filled with fun historically appropriate mechanics which
disturb status quo and snowballing. Ideologies causing revolutions, alliance blocs, world wars and cold wars, and/or new modern industrial economy mechanics which can make weaker civs grow rapidly and are object of rivalry.
3) AIs in diplomacy being like
"we are rational, scheming political players", no irrational agenda obsessions. AIs being agressive and expansive till the end, no boring and naive "end of history" thesis of civ6 and AIs being moralist pacifists.
4) Dynamic city-based happiness system which generates interesting
internal conflicts within civilizations (both civ5/6 had terrible city happiness systems).
5) Some interesting revolution in the way economic/demographic fundamentals of the game are done - something refreshing with cities, yields and pops. For example I would love "unstacked pops" as in pop units having ethnicity, religion, social class, needs, migrations physical location etc.
6) Balance between tall and wide (civ5 being too tall, civ6 being too wide)
7) Balance between gov system being too inflexible or too inconsequential (civ5 and civ6 extremes)
8) Some radically new religion system (civ5 and 6 had them almost identical)
9) Barbarians and city states being reworked into unified system of interesting minor faction "life cycle", with their own adventures, options to negotiate and assimilate them etc.
10) Reworked border growth mechanic, so my early era empires are not ugly city patchworks separated by nothing (petty I know
)
11) Fun statistics and fun replays, wealth of interesting data to play with
12) No agendas, governors, loyalty, era score, competitions, terrible civ6 world congress, gee I didn't like so many new and fun systems of the past game
Beyond that I am open for new and strange ideas, it's just lack of those that would make me sad. Just the first six points would make me very happy.