Adding jQuery to H5P seemed like a safe choice a few years ago, but with browsers being better and better at following standards even jQuery is not that needed anymore.
We should find a good way to deprecate jQuery from H5P sooner rather than later. Things to think about:
Warn creators of new content types not to use H5P.jQuery / offer a jQuery H5P library instead that they can use?
Deprecate the attach function and add a new one that returns a DOM element (could render be a good name?)
Make newRunnable accept both jQuery and DOM elements as its third parameter and deprecate the jQuery support there
Biggest operation that needs to be done to remove jQuery from core is perhaps rewriting core and the editor to stop using jQuery? Libraries can just add a dependency to a jQuery library instead of using jQuery from core.
1. No more jQuery in H5P core