Syncing styles
It would seem to make eminent sense to sync styles. Is that technically very difficult? One use case is where you've been modding a style on one side and using it in a document. You can't even work with the document on the other side unless you change to another style (which in a large document is costly).
If the loading of styles worked no matter where the style ID / URI pointed, posting the modded style on github would be enough to let them be loaded dynamically as well.