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

While not quite what you're looking for, "Acid Defender" is a WebAudio game that generates random acid house sequences as part of the game play:

http://cappel-nord.de/webaudio/acid-defender/