Hi there. I wish everyone a good day.
My suggestion is simple and nowhere overpowered.
The possiblity of Sword and board style for small shields and bucklers for all classes without having to pick Bard class for only grabbing Swashbuckler 3 enhancement. (Runearms and Orbs can allready use the style free. Why should not other classes be able to enjoythe shield bonuses ?)
Putting a restriction of Single weapon and shield style fighting to let the character use the style free with shield and medium sized weapon but not with any type of shield bashes to ensure the virtual focus at main hand weapon and the style.
Focus here is the Single weapon style and to let Main hand weapon get the SWF bonus while wielding small sized shields. Not Heavier shields and their bonuses; Not the shield bashes.
Right now, wielding any type of shield ,automatically, cancels Single weapon style although it is still Single weapon fighting while holding a shield without level 3 Swashbuckler. This can be as new martial feat that requires Single weapon fighting and Shield feats to get unlocked with its own bonuses and restrictions. for non Swashbuckler bard splashed Martial classes.
Thank you.
https://www.youtube.com/watch?v=xlYCxbBZUCY