You really should add the option to remove the third from the harmony.
There's a lot of music now that doesn't use it, and it would just be useful.
Thanks for your idea! We have no immediate plans to implement this, but we do listen to our users so we will certainly consider it if lots of people vote for it. Watch this space!
Actually every song has a third in every chord. If the guitar part is only power chords, the third is going to be played by a lead guitarist, synth, strings, or vocals. If not, the third is implied by the diatonic scale of the tonic pitch. To play open fifth "power" chords, which are not technically chords, just play the root and fifth.