@lthall’s presentation on Cooperative Lift from the ArduPilot Developers Conference 2025 is now up on the ArduPilot YouTube site.
Below are some direct links to some of the videos he showed in the talk
I should leave it to Leonard to discuss it more but my understanding is that this is still a work-in-progress but at least some of it, including the changes to Follow mode are included in ArduPilot-4.7 which will begin beta testing within a month or so.
Thanks Leonard!