While technically BLU is a mage class - it is much more than that - melee damage from blu is signficant. Additionally blu gets powerful job traits by setting spells - if blu could set 50 spells, nearly all significant blu job traits would be settable simultaneously. Also remember each spell has attributes associated with it. Being able to take advantage of 50 spells would require a significant increase in set points. While it would certainly be fun to do - the SE "balance" stick will prevent this from happening.