We don’t have any official recommendations, but there are a few people on the forum who have done this already:
As far as the software goes, since the secondary Pi is not dependant on FBOS for anything other than commands, you are free to choose whichever tools you prefer for the job.
OK, I was under the impression you wanted to call the “TAKE PHOTO” command (either via sequence + Farm Event or via external tool such as FBJS).
Once your camera issues are resolved, downloading the images off of the API might be a simpler solution and would not require a second camera (although there definitely are some users that still install a second camera).