I like this idea of advancing beyond line-based diffs into something more meaningful. If someone renames a variable/type/module/whatever which changes X lines of code across Y files, I really don't care to see all of that, for what I'm concerned with that's a single diff.

(Assuming the code is in a language with a good type system and without reflection, I'm confident in automatic refactors and don't need to spend time on them in code review)