I think shifting the focus to Colleen could make sense for the contemporary MCU. I've seen a lot of fans say Colleen was the best part of the Iron Fist show, and Jessica Henwick specifically said she passed on a big role in Shang-Chi in favor of the Matrix because she felt that taking the Shang-Chi role would mean giving up on a return as Colleen. And when asked about Charlie Cox returning as Daredevil during interviews to promote Glass Onion she definitely sounded like she would be interested in returning at least, if not having potentially already had talks about it.
The rumor from Daniel RPK says the project may be animated, and there were also rumors of a female Iron Fist showing up in Eyes of Wakanda, so that could be an animated Iron Fist show set in a historical period with a character like Wu Ao-Shi, Fan Fei, or some other historical female Iron Fist.