Would it be hard for the drone to be able to seamlessly switch between indoor/lighthouse tracking and outside/GPS tracking? How about the ability for the drone to orchestrate the battery swap autonomously with the charging unit? If you could add those two features you could produce a proof of concept video that would probably blow a lot of minds.
Seamless switching is definitely doable and shouldn't be hard, just need some time to implement. I'm using PX4 autopilot and it's very friendly for adding new functionality.
Orchestration is also close - in current demo both station and drone use Wifi to coordinate, so it's a matter of adding new logic.
Currently the most limiting resource for that project is my time :) I'd be happy if other people would want to join!
P.s. I think the I-term in your pid control loop is too high on your quadcopter, that oscillation isn't really affecting your flight control too badly but it heats the motors more than a stable tune would which reduces the service life of the permanent magnets in them.
Could be the P-term but the oscillation looks too slow for that, I guess one way to check for sure (assuming you don't have a blackbox on there) could be to increase your D-term and see what the response is