[AndyL]

Since this would require 11 steps to go from A to Bb, a 'swap sharp/flat button' would be handy.

Only 3 steps. A - Bb - C - Bb would give you Bb with flat chords. And swap would be Bb - C - Bb or Bb - A - Bb depending which way you wanted to swap. So the swap button isn't that necessary, although might be more obvious.

Andy