Hi Mate,
Few questions and things:
1. Snap 2 to 3 photos per second at full 5Mp resolution forever.
>I don't think the picamera reaches 3 FPS at full 5 mpix. I have achieved 1.6 FPS to a ram disk so I think to the SD it should be less than 1 per second. It is just a physical limitation.
2. Have a never ending record loop that deletes the first photo taken as the last one is written.
>Easy.
3. Be 99,9% reliable and robust. So barebones, minimal programming.
>Well... what I am going to propose to you is to use python or C# (I prefer C# mono, it runs a runtime but I have several services running since months without issues, one even runs in an australian motorplex to display karting results)
4. Run automatically upon boot. And recover in the case of a power failure.
> Easy. The main issue is with the Pi itself, if there are too many power failures = sd may get corrupted. Happened to me.