Two wonderful suggestions, rolled into one. Many people have been clamoring to see what the SK homeworld is like, however it is very clear that the game will continue to take place on Cradle for the life of the game. Additionally, I adore the suggestion of blind status, and wanted to frame a memorable way for it to be introduced.
Basically, the mission centers around a secret city on Cradle that appears reminiscent of a city from the SK homeworld. After dozens of knights, knights who were disgruntled or who had lost hope in the mission, abandoned their posts to live in the city, Spiral HQ classified the existence of the city to keep the rest of the knights focused on their mission. Recently, contact has been lost with the city. You, an elite knight, are tasked with leading a squad to investigate the situation with the city.
A big part of the mission deals with sight. There are a number of new blind-themed monsters, including blinding lichen and blinding polyps, blinding chromas with a new attack pattern (they spit a fast moving bolt of blinding sludge at you rather than leaving slime on the ground), and new wolvers/alpha wolvers that are invisible except when they are attacking. Additionally, traditional chromas, Ghostmane Stalkers, glob drops, and dust bunnies can be found on the mission. Finally, there are a number of new mechanics like invisible blocks, platforms, and secret paths (everybody loves secrets).
All of these things are meant to fit with the theme that the city is an illusion, a carefully constructed trap meant to lure knights to their doom. Their desire to return home made them ignore the danger they saw in the corners of their eyes. If you don't keep your eyes open, you won't see the danger before it gets you too.
1. why would there be only 1 type of grimlens in the city
2. if knights stopped living there, why would there even be a signal there now anyway
3. why couldn't someone just use the minimap to find their way?
besides that, sadly, I don't think OOO will ever add any new expansion missions :(