Or at least, offer a contextual menu "unified diff" that would work on a multiselection of files in the files panel (and on a commit, which would work as if all its files were selected).

Unified diffs remain useful for example for quickly reviewing small changes in a lot of files. One can repeatedly hit F6, but it can become tedious

Multi-file unified diffs are also useful for cutting and pasting changes (to an email for example).