I’m thinking of something like where you can choose exactly what gets synced. Like a specific set of settings/bookmarks/etc. that will be synced no matter what and not get overwritten.
One thing I’ve noticed that I find kind of annoying is that when using another device on my sync chain, bookmarks will be jumbled up, duplicated, and some folders will be empty with their contents on the top level of the bookmark toolbar.
I’ve seen other sync-related feature requests on this forum, such as Brave Rewards and extensions sync. Those would be nice too.