Code:
<Row>
<ModifierType>MODIFIER_PLAYER_ADJUST_UNIT_WONDER_PERCENT</ModifierType>
<CollectionType>COLLECTION_OWNER</CollectionType>
<EffectType>EFFECT_ADJUST_PLAYER_UNIT_WONDER_PERCENT</EffectType>
</Row>
The actual in-game effects of EffectType designations are coded into the game at DLL level, which is currently inaccessible to modding. It appears we cannot change which wonders are affected other than moving a wonder to a different era by altering a prereq civic or technology for the wonder. All we appear able to do is alter Qin's %, or create a copy-modifier with a different percentage for some other leader, but we don't appear able to alter which eras are affected. A search through the game's xml-files does not show any ModifierArguments, Requirements, or RequirementArguments other than those you have already found.