I always thought it would be interesting if MCH became the first debuff support job, so instead of buffing the party like BRD or DNC it would debuff the enemy. The jobs iconic kit kinda supports that style and it even used to have tools to that effect. Old hypercharge would increase the enemies damage taken and it used to have an ability called dismantle where they would just throw a wrench at the enemy reducing their damage dealt.

If they just built on that concept and made it so MCH provided a constant barrage of enemy debuffs in line with the kind of things BRD and DNC do for buffing the party it could be a powerful addition to the team.