BRD songs just need more flair and options during their filler. I also happen to like positive feedback loop rewards.
Under the condition of reworking the Soul Gauge so that it generates a lot more of it and Blast Arrow works differently, what if using Apex under Army grants the party X seconds of sprint tied to gauge spent? What if using Apex under under Minuet, adds X potency to each GCD for party members? What if under Mage it grants a budget bunshin to party's AoE attacks? What if Radiant Finale worked like old Foe's Requiem but also gave a steady regen to the LB gauge as well like Final Fantasia does? What if Battle Voice got back to what it used to do and doubled the power of any song being sung? What if Minne came with a Reflect attached to it as long as damage is suffered? What are they waiting for to give us pvp Warden's in pve? And that's just for raid buffs, which I find way more interesting than what BRD's currently does. Just replace the % boring passive increases with something like this that also requires active uptime with active Apex uses.
As for mechanical gameplay, what if only refulgent has a small cast? What if Refulgent actually generates gauge and repertoire moves like PP also give repertoire when used? What if Army's repertoire also increases Refulgent proc rate? What if Refulgent generates Harmonic stacks that allow a free cast of Harmonic past a certain amount? And I'm not even talking about bringing back the dots as a base for repertoire procs (it was so cool). Imagine all the new things to do during even the filler suddenly..
On DNC, well pvp happens to have that neat little thing called Dance of the Dawn. Perhaps this could proc from your partner actually doing good things and rewarding both of you. Perhaps Starfall should also grant sprint to both when used. Perhaps the partner damage bonus should be tied to Sabre Dance uses, just saying. Totally wilder but, imagine whenever you get a feather proc, the partner also gets one to spend with a lower random chance?
And frankly maybe you'd also bring a rphys because rphys jobs would have tools to generate LB faster. Or maybe LB would behave like in ultimates and not generate at all on its own but through the current actions that do, PLUS some new rphys abilities or mechanics. There is another thing rphys could bring, if they'd dare bring back damage types in an intelligent fashion, which would involve encounter design, where some mobs would have some resistances to specific damage types and rphys could manipulate this (probably comes with a lot of caveats due to duty finder, etc).