With the removal of Bardic Knowledge, I would like to suggest 'Bardic Expertise' to replace it. This is a small perk that allows a bard to pick a single skill focus feat into any skill they want to. While I understand that bardic knowledge was strong, the point of bards is to be the jack of all trades. This perk would become available at level 5, high enough level to want to remain pure, but low enough that you can see the benefits almost immediately for remaining pure.
Pros
-Allows bards to continue being jack of all trades, and be put on par with their contemporaries like fighters if they go the martial route, or bonuses to crafting, or bonuses to spellcraft.
Cons
-People might think getting +3 to spellcraft is broken. (I don't see how it is, bards still risk the x3 crit etc)
-Bards already have a large amount of skill points to do whatever they want. (Allowing them to hyper focus in a single skill doesn't break the game in any capacity and helps them beat certain thresholds. For example, crafting thresholds, necromancy thresholds, lore thresholds, that even the most hyper focused characters into said specializations still can't beat)
-Level 5 still allows the dreaded 8 bard / 2 fighter to exist / Grabbing +3 tumble for AC bonus. (One AC isn't game breaking and said AC is lost due to no uncanny dodge, so whenever flat footed, flanked, etc, that ac isn't there)
Counterpoint to bards having huge amount of skills.
In v5 bards had 5 skills per level. I assume it was to account for the performance.
Inv6 they get 6 skill points, so +2 to their vanilla 4. But compared to v5 they got a factual increase of 1, compared to increase of 2 in other classes.
I agree that an SF of bard's choice would be beneficial in choosing what kind of an inspiration you wish your bard to have.