Great idea. Here are a couple of libraries you may find useful to study

[Emasoft]

A crossplatform vector rendering library for C# is something we really need.

This is a crossplatform SVG library that does some work in this direction, but still incomplete: https://github.com/vvvv/SVG

It uses System.Drawing, but you can use a iOS/OSX Coregraphics implementation of System.Drawing here:

https://github.com/mono/sysdrawing-coregraphics

Many things are still missing, but it's a start.