The DJI Osmo (a stabilised camera)
mounted in a turret
Fairly obviously this is not a small modification, not structurally and not aerodynamically. Also one doesn’t really (usually) need the stabilisation on a camera which is well wing-mounted. What this gives you is a very nice ability to pan around.
I would prefer to have another person to be in charge of it 
Buy something you can attach your own camera!
Pay attention to the Mechanical-Controllable Range.
https://www.banggood.com/Feiyu-Tech-FY-G4S-3-Axis-Handheld-Steady-Camera-Gimbal-For-Gopro-3-3-4-p-995749.html?rmmds=search (for example)
DJI Osmo is way limited for this price…
Controllable Range Tilt: – 35° to +135°
Pan: ±320°
Roll: ±30°
Mechanical Range Tilt: – 90° to +150°
Pan: ±330°
Roll: – 50° to +90°
Yes; DJI stuff does seem overpriced in some respects, and we had a thread here but that isn’t the whole story; for example (from reviews) some of the others have a lot less power. IMHO, where you are supporting a mobile phone which isn’t going to be perfectly balanced, that is more important than a 360 degree movement which is OK for mucking about and doing funky stuff which few will watch more than once.
