For example, I have a set that could add flavor and balance to a decent, but plain civilization
Egypt: Unique Wonder Bonus: The Pyraminds
Effects: Enables all government civics
Enables all labor civics
City more likely to generate Great Engineer
Unique Ability: 'No Upkeep' for Slavery
Unique Improvement: Nile Farm: Farms +2 :hammer on regular tiles, +1 :hammer on River Tiles
Requires Civil Service
In CIV context, these things add amazing more possibilites. Made into a Civ-5, they could really define what civilizations are powerful. Of course, balancing might be a challenge, but if just Wonder Abilities were added, a world of new ways to play are as well. Plus, Wonder Abilities and wither one of the others would be a manageable addition in theory. The above is an example of how a civilization can still be balanced with these bonuses.
The List
Ottomans: Unique Ability: Seige can destroy Walls
Byzantium: Unique Wonder Bonus for Hagia Sophia
Effects: -50% Worker Time spent building improvements
No Missionary Limit
+50% Missionary Production
Obsoletes at Steam Power
Unique Ability: No religion modifiers (Adds a historical and balanced attitude)
Ina patch, if this proves too detrimental: Unique Ability: Maxed Religious Modifiers (+3, -1)
Unique Improvement: Aristocracy, replaces Town
Effecrs: Regular effects + 1 food (Adds a minor, but distinct push)
Japan: Unique Improvement: Shogun Castle, replaces Fort.
Effects: Regular effects + No City Raider Bonus on fort attacks
Unique Ability: +50% culture under Mercantlism
No city flipping under Mercantlism
Arabia: Unique Ability: 100% Missionaries Success in Cultural Borders
Missionaries have 50% if attacked (A minor, but slight push to help the bad civilizations)
Mongolia: Unique Improvement: Ruins, replaces City Ruins
Effects: +200% clear time
+1 WW for each ruin against enemies
Mali: Unique Wonder Bonus: University of Sankore
+5 beakers from all Religion buildings
City more likely to generate Great Scientist.
Ethiopia: Unique Ability: Nearby Mountains increase :strength 5% each Peak
Inca: Unique Improvement: Terrace, replaces Farms, available at Masonry
Acts as a regular farm, except:
+1 :food on hills
+2 :food, 1 :hammer on Mountains
Unique Ability: Workers, Scouts can use Mountains; +5% beakers for each civlization not met in by 500 B.C., decreases as more civilizations are met
Greece: Unique Ability: No Emancipation anger
Unique Improvement: Maritime Colony Waters, replaces Fishing Boats
Doesn't consume Work Boat at first use
Rome: Unique Improvement: Raven, replaces Fishing Boats
Causes Collateral Damage to enemy ships and units inside if landed on
In a patch, if this is way too weak this could be added: 2 turns to pillage