Hi Jim, if I were you, I'd forget about head tracking. I've got V1 Predators and a pan/tilt system all set up, but I NEVER use head tracking. Pretty much for the same reason you don't look out the side windows much when you drive a car. I have had it going while flying, but didn't move my head. My conclusion is that it's a novelty feature - something to show off to the people you might stick the goggles onto. It's just not practical for actual flying.
I don't think any Fatshark goggles have the headset battery voltage on the display. Not that endurance is an issue. I've had sessions where I've run my 5 2200s through my Bixler and I think I put 300Mah back into the headset battery. As for an OSD for the on-board system, that's an add-on that goes between your camera and video transmitter.
The cameras that come in Fatshark combos are poo. They are CMOS, of which I've never seen one that comes close to a CCD camera for FPV performance. You can put a wider lens on it, which improves the general amount of light that gets in and thus there's less to do for the camera to adjust to different light conditions, but CCD cameras are just so cheap. BMSWEB seems to be happy with the V2 CMOS camera with the wide angle lens, and he uses one of the best CCD cameras available, so it can't be too bad. If you're thinking about replacing a Fatshark camera with a CCD, note that they generally run on 12V rather than 5V. This means you have to adjust the wiring to power the CCD camera - it won't work with the 5V out from the video transmitter.
Head tracking can be added on to the V2 goggles. It's an expensive add-on though. I'd forget head tracking and just go with what seems to be a solid system in the V2 Predators.