ggplot colour bar with 2 scales (top and bottom)

I am trying to make a ggplot2 with a colour bar with two scales (or two sets of labels) on both sides of the colour bar (for example having both a cm and inches scale on the left and right side of colour guide bar or having Celsius AND Fahrenheit). Is something like that possible in ggplot2? See picture for what I am looking for (ideally, in this small example I would have the numbers 1:5 at the bottom of the bar and the letters a:e on the top of the bar). Could I make two legends and just overlay them somehow? also having a title on the top and bottom would be helpful

df <- tibble(A = letters[1:5], B = 1:5)
  
ggplot(df, aes(x = A, y = B, fill = B)) +
  geom_col() +
  scale_fill_gradient(high = "blue",  low = "red",
                      labels = letters[1:5],
                       guide = guide_colorbar(
                         direction = "horizontal",
                         title.position = 'top',
                         title.hjust = 0.5,
                         label.hjust = 0.5,
                         legend.location = "bottom",
                         label.position = "top")
                      ) +
  theme(legend.position = "bottom")