Yes, you could, although it's not a perfect fit right now as the only data structures you get in matrix are a timeline of arbitrary objects (events) for a room,

Yes, you could, although it's not a perfect fit right now as the only data structures you get in matrix are a timeline of arbitrary objects (events) for a room, and a key-value map of arbitrary "state" events. This is flexible enough for many purposes (and you could probably use them for issue tracking and PR management), but we can't efficiently store arbitrary object graphs or trees yet. It'd be great to get there though; meanwhile there are other projects like IPFS and IPDB which are active in that space too.