Poor monk.... will no one give us blunt debuff??

One of the suggestions that would be a bit better than redistributing the buffs would be to change how some of them work entirely. As well as your suggestions introduce new problems. Just like DRG is pretty much mandatory right now because of the piercing debuff they bring, BRD under your suggestions will have an always include position in a group given they could have the slashing debuff no one else gets in addition to the other plethora of utility buffs they have. Additionally if the damage debuffs are cross role skills, I would expect, especially in roulettes and 24-man content, no one will take these skills.

So here's another way to handle that:
remove blunt resist down, slashing resist down, and piercing resist down from the game entirely. Replace the skills on all jobs that have them with magic resist down and physical resist down. My suggestion is to distribute those skills between samurai, monk, dragoon, and ninja with magic resist down going onto ninja and monk and physical resist down on dragoon and samurai.

It would create a situation of one of two melee jobs for each slot, but it does change things from the pretty much mandatory DRG/NIN load out, but still leaves raid groups alone that are currently running that combo.