[@Crab Bane] I'm not against setting the RP during the time of the Created. Since Infinite isn't out yet and there is only limited lore of what is going on in that time, though, we'd pretty much just have to accept that we'd be making up things to happen that may not be lore friendly. I am fine with that, if that's what you and the others want, it's just something to consider. That would give us more creative freedom with our story.

If we go for other time periods, I think there are a few of ways to justify joint operations. A powerful enemy, or something very important would do it. For example, when the Ark's monitor went crazy and tried to activate the Halo array, they sent a joint team to stop it. Also, along the border of UNSC and SoS space, there is an area called the Joint Occupation Zone, with colonies governed by Humans and Sangheili. If Jul 'Mdama's Covenant or another faction made an attack there, I think it would make sense for both militaries to respond together. I think it all depends on the "scale" of the stakes we want to go for. Halo games usually portray "fate of the galaxy" sort of threats, and that can certainly be fun to do. We also have the option of bringing the stakes down to something like individual planets or settlements. We could be a specialized team working, essentially in peacekeeping, against raids and insurrection from the Covenant or rebels. It's a smaller story, but it could be more personal.

I do like that Sangheili design, as well. It looks like an ancient, or maybe ceremonial sort of armor, with a variation on a curveblade.