Diversion in place of Tactician.
Knock-back resist would be nice, but it's manageable without (a long-range holmgang style bind minus the invuln could be a fun idea).
Better AoE options. 4.0 bard AoE is depressing. I never play it in dungeons anymore. Mobile long-range Wide Volley, gone. Flaming Arrow, gone. Rain of Death procs stilted to a paltry 30s every 80s.
Seen some mentioning Foe/Sidewinder/AP changes, I'm impartial mostly there. I appreciate AP being a variable phase to play with WM burst alignments and as chill phase to rest from a full minute of proc + other ogcd nuttiness. Maybe something offering more freedom in song rotation/arrangements, but I'm at a loss for ideas there.
Self-sufficient piercing could be nice, not having a flat percentage of potential damage output locked behind a single job...but I'd still be itching for a dragoon for their Battle Litany (SCH too, of course ).
What I would love most? A 90s ogcd that readies a Straighter/Refulgant proc. Nothing makes me mentally curse RNGesus more than not getting a proc with Barrage use. Heck, make it available only for (re-) openers worst case. But I want this muchly.
Otherwise, 4.0's bard rework was an impressive return to form from their stint with arrowmancy.