The main issue that would prevent me from using this editor is that every object is rendered as 20px × 20px regardless of the aspect ratio. For files it looks like the width and height can be obtained using an API request (multiply the width by 20⁄height to get the display width), and for text and filler cells you can use the definitions in the {{Routemap}} CSS.
xingrz
commented
4 years ago 
I tested this editor using the diagram code of w:en:Template:East London Line RDT.
The main issue that would prevent me from using this editor is that every object is rendered as 20px × 20px regardless of the aspect ratio. For files it looks like the width and height can be obtained using an API request (multiply the width by 20⁄height to get the display width), and for text and filler cells you can use the definitions in the {{Routemap}} CSS.