A common problem I encounter with my paper notepad is that it tends to be filled chronologically. Whilst this is useful for somethings, it does not allow grouping of notes by topic.
An alternative approach that does allow notes to be re-ordered chronologically would be loose-leaf sheets. This is in fact how I took notes back in college, with those sheets being added into the relevant lever-arch file. But such an approach is not common in a professional setting despite its benefits.
There are a couple of reasons for this: firstly, the volume of notes professionals take is typically less than students, so level-arch files are too large; and secondly, there is no professional-looking stationary for performing such a function.
The latter point suggests a opportunity, to create a paper tool that combines a pad of loose-leaf sheets with a tabbed organiser that the pages and be quickly and easily added into. This could be for example a (slightly larger than) A3 side leather folder with a seam down the middle. The right side (for right-handed people) holds a pad of paper, the left holds a ring-binder with tabs to drop the pages into.