Your proposed leader traits look
really good: fun, interesting, and full of flavour. I've suggested a few balance changes below; but, honestly, I would be quite satisfied keeping your first draft as is. (Don't get me wrong: the traits aren't balanced in the sense that they are all equally powerful. That would be impossible. They are, however, balanced to the extent that they are all genuinely attractive options.) In fact, I have nothing further to say about the Aggressive, Charismatic, Diplomatic, Financial, Imperialist, Industrious, Judicial, Progressive, and Spiritual traits; that's half of them right there! As for the rest:
Suggested
CREATIVE
• Allows 1 Artist specialist per city
• +50% Wonder production
• +1 happiness from Theatre
,Tavern
ENTERPRISING
No suggested trait changes.
Trading Post gives a free Navigation II promotion.
EXPANSIVE
• +1 food per city
• 50% faster production of Settler
• Double production speed of Harbour
, Sewer
HUMANE
• 100% longer Golden Ages
• +2 health per city
• +1 happiness from
Aqueduct, Bath
ORGANIZED
No suggested trait changes.
No Assyrian, German, or Zulu leaders. Ashurbanipal and Frederick are reassigned leader traits.
PHILOSOPHICAL
• +100% Great Person birth rate
• Double production speed of School
• +1 happiness from Monastery
PROTECTIVE
• Double production speed of Granary
•
March promotion for Melee, Archery, Gunpowder units
• +1 happiness for Walls, Castle
Also,
Walls and Castles do not go obsolete (for anyone.)
TACTICAL
• All Military civics available
• Combat I promotion for Melee, Mounted, Gunpowder units
• +100% gold upon city capture
TRADITIONAL
• +5 happiness for Palace
• +1 free specialist per Wonder
• +2 culture per specialist
Notes
CREATIVE: +2 happy/city is a good trait effect. Charismatic leaders begin with it and many others can reach it with the right buildings. Creative, a weak trait to begin with, had only +1 happy. Adding the Tavern improves balance.
ENTERPRISING: Both Viking leaders are Enterprising. The Trading Post UB currently gives Navigation I for free. Can you say 'redundant'?
EXPANSIVE: Did you overlook this suggestion?
HUMANE: See
Creative. +3 happy/city on an already strong trait is too much. Removing the Hospital improves balance.
ORGANIZED: The Karum, Rathaus, and Ikhanda already reduce city maintenance costs. They would be too powerful in combination with Organized.
PHILOSOPHICAL: Philosophical can't compete with all the new and improved leader traits. The bonus GPP only matters in the few cities that regularly produce Great People; and the building discount doesn't come into play until the Renaissance! +1 happy/Monastery helps round out the trait: it fits well thematically, encourages players to acquire multiple religions for multiple monasteries, but can't be abused because monasteries eventually become obsolete.
PROTECTIVE: I am least satisfied with the Protective trait. Giving units both the March and Sentry promotions makes little sense: are they mobile, lightly armed reconnaissance divisions or massive, heavily armed regiments prepared for long foreign campaigns? Since neither Melee, Archery, nor Gunpowder units can normally take the Sentry promotion, I suggest you cut it. (I would still like to see free Sentry promotions in the game and I have some idea where. Stay tuned.) Meanwhile, +25% defence makes little difference to mature cities with Walls and a Castle. It doesn't make much difference for newer cities, either, since it can be so easily reduced to zero. Once again, I suggest double speed Granaries for Protective leaders. It gives them some economic power and does make a difference during city sieges. (If enemy units have camped on your food sources, you can survive on the +25% food saved for a few turns while you clear them out.) Frankly, I would prefer something even stronger: maybe a free Granary in every city. Finally, Protective leaders should not lose their +2 happy/city. (None of the other leaders do.) Since Gunpowder units ignore Walls and Castles anyway, I suggest that these buildings never go obsolete (for anyone.)
TACTICAL: Thinking about it, double speed Barracks and Castles aren't terribly useful. Barracks are only needed in military training centres; Castles, in border cities vulnerable to attack. +100% city capture gold is much more interesting. It contrasts nicely with +100% pillage gold: Aggressive leaders are raiders while Tactical leaders are
conquerors.
TRADITIONAL: No unhappiness in the capital is problematic for a number of reasons. It can easily lead to very unrealistic size 20 capitals in 1000 BC. These monster capitals would generate far too much commerce and production via the Monarchy civic. Furthermore, players would be discouraged from developing their infrastructure: there's little point in building Stadiums, Theatres, and Temples if you don't need the happiness. +5 happy/Palace keeps the bonus at a more manageable level. (As a side note, I worry that +1 specialist/Wonder and +2 culture/specialist will make Cultural Victories too easy. Put another way, it may not be possible to conquer a Traditional leader on another continent before (s)he wins by Culture. What do you think?)
Edit: My mistake, I did want to mention one more trait.
SPIRITUAL
No suggested trait changes.
Shwedagon Paya gives +1 food/state religion building.
I've said it before:
With the changes to the Spiritual trait, this religious wonder becomes pointless for the very leaders who should be eager to build it. I suggest changing it to +1 food/state religion building, filling a natural gap left by the Apostolic Palace, Spiral Minaret, Sistine Chapel, and University of Sankore.