We're working based on SVG 2 and basically ignoring SVG 1.1.
I was unsure about the best approach here, so I asked Nikolas Zimmermann (original author of SVG support in WebKit) and his advice was to do exactly this. :)
I was going to ask if you were prioritizing the SVG 2 features that are already implemented in Chrome and Firefox. But it appears the W3C has removed a lot of the new ones I remember from the spec (path data bearings, mesh gradients), and that both Chrome and Firefox have implemented a good amount of the existing spec like tabindex and friends.
(Ok, here's one-- "inline-size" and others for doing auto-wrapping text in SVG. Looks to be unimplemented anywhere.)
I was unsure about the best approach here, so I asked Nikolas Zimmermann (original author of SVG support in WebKit) and his advice was to do exactly this. :)