-A chord sequence tells you at a glance the harmonic structure of the song regardless of key.
-Studio one now pretty much knows the key you are in so implementing this wouldn't be too hard.
-The harmonic content of a song in many ways tells you more information about a song than seeing a series of chords.
A couple of popular progressions in the key of G. The sequence produces a similar emotional response regardless of key.
When improvising in a song where the key has been set a box could show which chord and which note is being played. This would be excellent for improvisation as it would give you an idea of the feeling you are closest to playing. Each interval (and chord) has a particular mood or feeling. The interval of the 5th for example evokes an open, balanced expansive feeling. The 4th is clear and wide awake. The 7th has most tension and wants to propel the music forward.
It would also be good if a version of the chord wheel could show live input of note data (the chord you are playing) at all times. The box mentioned above could show all this information. All the chords in the key of the song could also appear lighter or in different colour on the chord wheel.
Being able to change the key of the song from the chord wheel would also be excellent. The key of song display could change when a song with key changes is analysed. You could also record key change information into the chord track.