Let me try to set things straight here.

The simplest solution to make it feasible for Blue Mage to participate in all content is to utilize a tool that SE has already created: Basic Instinct.

Allow Basic Instinct to be used for the Masked Carnival and the Blue Mage Log, in addition to the normal solo duty rule. This would be essentially identical to current Blue Mage. Everyone who is satisfied with the current Blue Mage can continue to enjoy it the same as always.

In any situation where Basic Instinct can't be used, which would be all other content the game has to offer, including Duty Finder, Blue Mage would essentially be "toned down" due to the absence of Basic Instinct. Certain spells that would be considered game breaking would no longer be an issue because those spells would be made reliant on Basic Instinct to achieve their full strength.

Nothing has to be removed. Nothing has to be cut. It's entirely possible for Blue Mage to remain "as is" while simultaneously opening the door for more players to enjoy it.