Now as we know the equipment of the Roman infantry changed a lot from 231 BC (start of the game) up until and throughout the Imperial era.
Around 100 BC the Marian Reforms brought forth the standardization of training & equipment within the Roman army, making sure each soldier was equally trained & equipped. The result was a highly skilled professional army the likes of which the world had never before seen.
Not long after, at around 50 BC (exact year is debatable), the Lorica Segmentata was introduced, a highly advanced type of segmented armour that provided the wearer with both superior protection & flexibility compared to all earlier types of armour. Now it is generally accepted that this type of armour had become standard equipment by around 100 AD, during the conflict with Dacia, however when should we be able research it in Rome II ? Should we be able to obtain it earlier or should advances in technology like these be restricted to certain time periods ?
Marian Imperial Roman Legionnaires ca. 100 AD: