Bingo, I need this too. Cams without 24 fps are useless to me, since you can't mix it with movie footage. That's what I used the first Yi for. For the life of mine I don't get why they don't offer 24 fps on the Yi 2. Hell, I would order 6 cams to shoot 360 degree VR videos if they could do 24 fps, but no.
In firmware 1.3.3 there is 4K Ultra 24 fps.