All it needs to do to feel like every other Final Fantasy Blue Mage is learn enemy skills through a passive or active interaction with them. It already does this.

Exploiting Dark Cutter and Level 5 Death ala FF5 speedruns is not the gameplay most people engage in when using the job in its many many iterations. There have been iterations where it had limited to no exploitative nonsense, and nobody complained. The only iteration that had more than a handful of spells was FFXI's and while that would be *nice*, most of us understand that it would create a logistical nightmare to balance, and are okay with a model more like the majority of its appearances.

Saying "It will not happen" is opposition for opposition's sake.