This is just a prof of concept; But i think it's pretty cool. Rls is pretty fast, so we won't see long running notifications, at least for small projects that i tested.
I know jdt-ls (Java language server) aren't that fast. So this concept might for that (Which i hope to finish soon)
Open question; why don't we have API for Ide.Notifications.from_object(), or so, so we have an easy way to retrive notifications, just like the easy way to insert?