Integration of GeoGebra applets
GeoGebra is the one computer algebra system with geometric and statistical apps as well that is used in education world-wide, and like H5P it is open source as well and has a large and growing community.
How cool would that be for math teachers: Embed GeoGebra applets like https://www.geogebra.org/m/PQgbhrES in H5P interactive videos. Maybe it is not that difficult to implement because these applets can be embedded in normal web pages.
A good example of how that could work is how it is implemented in Office Mix.