A just-announced Halo: The Master Chief Collection mod project is working on a full singleplayer and cooperative campaign in the style of Halo: CE and Halo 2, and has released a trailer, statement, and screenshots that are pretty promising.
The trailer does some flyover shots of what might be the destroyed colony world of Reach before transitioning to the familiar environment of the Halo ring, then showing off some unique takes on the older covenant alien designs.
The RedShift team, a seven person group called Blimp Brigade, described their project like this on ModDB:
"RedShift is a large open-ended Halo campaign that can be played either solo or cooperatively with up to 4 players. This is a brand-new campaign. All of our levels are being made from the ground up, with a completely unique story and new set of characters. While we are drawing our inspiration from Halo: Combat Evolved and Halo 2, we are particularly looking far beyond the world of Halo to make sure we have an experience that is completely unique," they said.
Rich, the project lead, was previously known in the Halo modding community for working on a mod called Halo: Composition, which was in on-and-off development from 2012 to 2019. Rich says that "all of the good ideas from Halo: Composition have been integrated into RedShift."
"For example, the first level in Composition was set to be an autumn level, just like Redshift and most of the level/play spaces were ideas I had already worked out on paper and was easily able to make those designs compatible for RedShift," said Rich.
"This means that a large chunk of the play spaces in RedShift did not have to be thought up from scratch, which was a huge time saver."
You can find Halo: RedShift on moddb.