I found a way! It's still a manual process but better than nothing:

• Copy your Sketch designs as SVG code from Sketch V
• Paste it in a text editor and save a .svg
• Open the .svg file in Sketch V-1

Tried this from Sketch V41.2 to V38.2

I find the idea very interesting; being able to add a layer of customization on top of vectorized illustrations to interact with them and create infinite different versions of it in a few clicks/slides really takes the SVG to the next level. Also, even though you seem to require some CSS/JS input, your documentation is pretty clear for a non-developer: I especially love the possibility to interact instantly with all the examples available there and in the galleries.