Someone brought this idea to my attention:
An open-world game focused on the Covenant, pre-schism. You could play as an Elite, rising through the ranks as you fight Humans and collect Forerunner artifacts.
I actually like this idea because the Covenant hasn’t been explored in-depth yet and there could actually be room to make it work within the lore.
I’m not sure if this should be here or in the general discussion.
They made a game focusing on the Covenant where you play as an Elite, fight Humans and collect Forerunner artifacts.
It was called Halo 2. 
> They made a game focusing on the Covenant where you play as an Elite, fight Humans and collect Forerunner artifacts.
>
> It was called Halo 2. 
You didn’t really fight humans but I get your point. That game, however, wasn’t open world and explored one Elite more than the Covenant as a whole.
Bungie actually considered making a Halo 3 expansion which would focus on either an Elite Spec-Ops squad or the Arbiter, overtime though they settled on an ODST squad and henceforth it became Halo 3: ODST.