We also have a category for projects that are focussed more on abstract community resources / engagement, e.g. the creation of new content / update of existing content in this platform or review/update of existing addons that are no longer maintained by their original developer.
There is no restriction on the number of suggested ideas that you can add. Some project ideas may not attract other interested participants, so you may choose to drop (some of) your own suggestions and join a different team on the day of the hack-a-thon. We will definitely not force anyone to work alone on a project just because it was their idea