Currently the naming of civ specific champion and mercenary units in the templates/units/ folder is rather inconsistent; it appears to be designed at a time when all factions were supposed to have only one infantry champion and one cavalry champion. The current naming scheme makes it hard to add new champion units; e.g. Athens has the following champion units:
athen_champion_infantry.xml athen_champion_marine.xml athen_champion_ranged.xml athen_thureophoros.xml
This patch applies a consistent naming scheme, similar to how citizen soldier templates and champion actor art files are named, which makes it more suitable for future additions and mods; e.g. Athens' champions are now named:
athen_infantry_spearman_champion.xml athen_infantry_marine_champion.xml athen_infantry_archer_champion.xml athen_infantry_javelinist_champion.xml