Before SSL 2.0, you could modify an XML to override the buttons/knobs on a controller with Native Support in Serato Scratch Live.
After SSL 2.0, it was nearly impossible until I figured you could hijack the MIDI input using the FREE MidiOX software or Bome's MIDI Translater. You would leave the MIDI output alone to get the HID and LED button lights support in SSL.
I finished the Custom MIDI Mapper XML for the DN-S3700 and Serato Scratch Live. I will now work on updating the PDF and create a video. With Scratch Live 2.5.0, Serato added enabled MIDI out so your precious buttons will light up.