The Amurite Palace does provide Enchantment mana, along with Meta Magic and Dimensional mana. (In vanilla FfH it provides Meta Magic, Fire, and Mind, but since Kylorin was trained by both Ceridwen and Nantosuelta I considered it thematically appropriate to change that a long time ago.) I honestly consider Enchantment 1 to be rather week benefit, as the Tower of Alteration grants enchanted Blade to all eligible units in the city anyway. Also, Firebows (another Amurite UU) already start with Enchantment 2, and Wizards start with the Spell spheres that would otherwise be produced by the Enchantment 3 spell. Giving out Water 2 or Earth 2 without mana would be much more overpowered. I'd be more likely to give the Arcane Guards Meta magic 2, mostly to let them dispel rival magical buffs although resetting mana types seems to be the spells more common use.