2 out of 3 points should not be in the list at this point of time.
There is no browser around servo that is usable and they start with accessibility?
The effort should go first to have it work as an everyday browser and get as much market share as possible. Then think of accessibility and WebView Integration.
This is a unique opportunity to have a browser engine not depending on Google, Microsoft or some of AI companies wanting to get into this field. By watering it down, you will just lose the market to the ladybird which is focused.