I'd love to see a Support Ability that makes a unit immune to any statuses they are able to inflict themselves. So a Wizard would be immune to Frog, Poison, Dead... and Holy Knights would be immune to Stop, Death Sentence, Dead, Silence, and Confusion. And Math Skill should not apply.
Not a revolutionary ability, but I think it's new and not too overpowered. Sure, an Oracle would then be immune to a lot of statuses, but it's not like the ability would make them invincible or anything.