So you can write on the checklist of things html5.5 or 6 or whatever needs:

* Local config storage (doable in cookies or localstorage)

* Local save storage (probably too big to fit in 5MB of localstorage)

* Mouselook (mouse buttons work fine). I think you can already do this though, I know you can at least track cursor position and you can implement mouselook off that.

* Mousewheel in firefox, at least, wasn't rebindable.

* I see problems in fullscreen browser games that take every single browser button and override it, so you would probably want a "you can't rebind this key" key. If there isn't already one.