Idea for an opensource project: a disk space analyzer (like `dutree`) that is able to analyze not only directories, but also packages managed by various package managers. It should contain specialized code for each of supported PMs and give suggestions on which commands to use to free up space.
And also, some smart planning tool may be included, which might be able to answer questions like "I want to free up 100GB but keep firefox and my downloads folder intact, what to do?"