I'm curious how you handle the things that are between SVG specs 1.1 and 2. Because AFAICT both Chrome and Firefox decided not to implement SVG 2. Yet both have grabbed a common selection of changes from SVG 2 and implemented them.
E.g., myRect.style.x = '50px' will work in both Chrome and Firefox, even though SVG 1.1 doesn't allow for this because "x" isn't a presentation attribute (and only presentation attributes are supposed to have corresponding CSS properties).
Relevant to animations-- the fact that Chrome and Firefox allow most (all?) SVG attributes as css props lets the user do a nice end run around SVG animations. They can just treat the SVG objects as if they were HTML and use the web animations API to animate them.
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.)