How can we extend FileImageSource to accept SVG files?

Many components of Xamarin.Forms use FileImageSource as a parameter for icons.
For example ToolbarItems passes the string to an instance of Xamarin.Forms.FileImageSource.
All my icons are in SVG format, and I don't want to convert them to dozen of ugly bitmaps versions for each devices.
I already use a component that render SVG files ( https://github.com/paulpatarinski/Xamarin.Forms.Plugins/tree/master/SVG ).
It's a class inheriting from Image class ( SvgImage : Image ).
How can I extend Xamarin.Forms.FileImageSource to accept SVG files and render them using the SvgImage class?