I purchased a 2006 six pac s650 from an older couple that barely used it. I bought it for the size of the beds and relative simplicity of the camper for when Im towing my off road car into the sierra...
Think I'd go with a compressor fridge like a Nova-Kool or a Waeco compressor unit. Not sure without extensive modification if you could put in a water heater or oven. We have gotten by with no oven for years and out old / sold Lance had one that was just used for storage anyway.