I checked the code, it's probably as simple as rewriting the `src\scripts\app\utils\default-instruments.js` file and replace the samples. Presets won't work because they rely on the ID string.
I have like 100GB of samples, it might take a while :)
The key here is to pick chords and pads from the same scale.
I'm bit busy now, but on the weekend I might give it a shot. If I make any progress, you will find it here: https://github.com/tiborsaas/djent
http://cappel-nord.de/webaudio/acid-defender/