1. some of your Generals will get massive boosts of traits like cavalry commander or seen the elephant, atm i have a Pahlav FM with 5 normal stars and 14 stars wen attacking Hellens with a certain amout of cavalry :D

4. well phalangites wielded 6 m long sarrissas whereas Hoplites wielded the much shorter Dory the hoplite phalanx better represented with a shieldwall/very dense formation there are some minimods that deal with the problems of hoplite warfare.
in other words: because it's more realisic :P