Tonic finder / chord placement
The piano sheets are currently not very useful because no-one plays the chords this way.
For example if you are in C, you play G (dominant) below C. But if you are in G, you will probably play C (subdominant) below G.
Given the song does not change the tonic in-between, it is not hard to find the tonic chord: Test every chord which appears and count how often its IV, V and vi appears.
This way it would also be possible to give the real chords instead of enharmonic equivalents.
Dear Anonymous, this is a nice idea, we’ll keep it in mind.