I say keep it mostly as it is since MCH being the simple job is one of the things it is meant to be for those who prefer a DPS job that is not overly complicated or expect you to constantly keep a eye on your job mechanic and rotations.

Things that need to be changed is the Flamethrower as it is a very useless skill to have. Update it into a 2nd DoT skill that apply burn DoT condition.

A new thing they can add in the future is maybe give MCH a Power Armor mechanic that has the MCH temporaily gain a power armor which updates their skills to Power Armor skills for heavy Burst Damage that can rival a Black Mage burst damage or greater if managed right. Access to the Power Armor can be based after using the Queen once or twice, the MCH gains the abiltiy to fuse with the Queen to obtain his/her power armor for this burst mode attacks until all energy is spent.