Since the dawn of time, people have been wishing for haki upgrades on Law and Kidd, but not a single one has considered how such upgrades would benefit their combat styles... Long story short, they are incompatible with haki and nothing would change.
Even if you straight up handed them the power of handful of the very strongest, they would still remain High Tiers.
Their known abilities cannot benefit from Haki. That's why their haki feats are trash.
