Get the B2 power. Excellent flight time.Yeah this would be cool. I own the bebop with skycontroller, the recorded Video is awesome. But one need several batteries because of 6min Flight Time
One more: Make the gyroscope a full compass, costs maybe 50ct. Knowing the drone's direction would enable all kind of cool things when combined with the phone's GPS. Including follow me, orbit me, where has my drone crashed, flight plan, flight log with map, ...SD card slot.
I would even be happy if they just enabled video storage on a tiny USB stick fitted to the existing micro USB slot. They could easily do this as Tello already supports USB OTG and FAT filesystem.
I they want to blow the competition away without breaking the bank: 180deg fisheye camera like the Bebop has. just imagine you had 180deg free headtracking in this little drone.