It’s on the list.
The WK default colours are meant to be shown on a light background. On a dark background they look bad. The Dark Breeze theme in the app was specifically requested to look like the popular Dark Breeze theme for the desktop site, so that’s where the colours come from.
I can always add another theme if there’s enough interest, but as far as I know most people are content with the Dark Breeze theme as it is.
There is, but it’s disabled by default. Look for the special buttons in Settings -> Advanced -> Other. You can assign various functions to them.