Feel free to give suggestions on how it can evolved from a Limited Job.
Probably its biggest issue is literally in how a Blue Mage Functions, they'd have to give it fixed functions which could step on the jobs identity., which can also hurt the Job.
This isn't an easy fix, the current idea is Solid....for a start. But then its limited afterwards. The latter, giving it fixed skills could ruin the Job itself because then its pretty much a glorified Black mage. Not to mention the amount of Balancing they'd have to do to consider making it a Hybrid job: if it keeps Might Guard.