Maybe very small local cells to improve connectivity in difficult landscapes (mountains, skyscrapers, underground)

Something like this would've been useful in a couple remote networks that I worked on. Internet was easy to get with some ubiquiti wifi routers and antennae. Getting cell reception was a pain in the ass that involved setting up a repeater in the one spot of the valley where reception was kinda okay. I haven't looked into the project too much, but I imagine I could set it up to connect to a telcom tower and handle the wireless backhaul similarly to how I did the wifi.

Edit: An open implementation like this could lead to cheaper cells for large, concrete/metal buildings that typically have terrible reception.