Include link to diff of all code changes
If the project uses github (or similar) and it has tags for the releases, it would be possible to include a link to a page that shows a diff for all the code changes between the two releases. eg this link (https://github.com/twilio/twilio-python/compare/5.6.0...5.7.0)
Even better (but would require a new service) would be something that automatically shows a visual diff between two given versions of the downloaded source from PyPI. That is, it would be a real release comparison, not one relying on accurate tags in the repo.
That's an interesting proposal. I'm going to run some metrics on this as I'd like to find out on how many projects something like this would be possible in the first place.