Currently in 0 A.D. the Seleucids have five champions (pikeman, swordsman, cavalry, chariot, elephant), but players have to choose between “traditional” (pikeman + chariot) or “Romanized” (swordsman + cavalry), so effectively they have only three.
Historically this doesn't make sense, since heavy cavalry was used in combination with pikemen; e.g. at the Battle of Magnesia (190 BC) the Seleucids fielded c. 16000 pikemen and c. 8000 champion cavalry, as well as scythed chariots and war elephants (Livy 37.40). Therefore I for one would be in favour of removing this artificial choice.