Flamestrike
Legend
And can switch your style every four levels, which increases it's power.
Not from the feat alone you cant.
Only when you get an ASI increase from the Fighter class can you swap a an ASI you know with one available to Fighters. You can do the same thing as Ranger or Paladin as well (when you get an ASI from one of those classes) but its limited to F/S known by that class.
Swords bards will also need to MC to Fighter, Ranger or Paladin for at least 4 levels to swap their F/S out.