So what's better than a highly proficient skirmisher unit with good armour? a highly proficient skirmisher with even better armour, hitpoints and even deadlier accuracy to boot! for the Celtiberians, the Scutanann skirmishers can be upgraded further with the addition of better armour and more professional training as part of a standing warrior élite, making them tougher and deadlier in the face of more stalwart opposition and even deadlier weapons.
Scutanann Loricati, being a rung up from regular Scutanann, are thus logically more powerful than their unarmoured forbears. While they are still essentially semi-mercenary professionals, the addition of chainmail makes them ever more powerful, capable of receiving cavalry charges and softening up melee infantry in anticipation of a massive push against the enemy. Use these men to hold your lines and to complement your melee infantry, particularly Hostatir and Lanceari (if available).