In order to make Blue Mage into a regular class, they'd need to overhaul it entirely.

Just for starters, the entirety of the Blue Magic Spellbook would need to be removed, they'd just learn a set of specific spells as they level like a normal class would.
Most of the spells they have would lose their effects. Just a simple DoT or two, maybe a short 5% Vuln up with a 60 sec CD...

If they started to try turn it into a regular class, it'd probably be just about what Summoner is currently, except no Egi or trance.