I don't think it's crazy, plenty of people in forums have talked about how they've used inverter's in their priuses to do the same thing. The only thing to be cautious and aware of is that when fridges start up their compressor, they take in more initial current (for a small fraction of a second only) than they're rated at. The older the fridge, the higher the starting current could be. It's possible for you to turn on the fridge (say 800W), then turn on a series of lights (600W worth), and get a runtime of current around say... 1400W and think everything is fine. But, when the compressor on the fridge cycles off, then back on again later, it could temporarily overload the 1500W limit on that cycle on, thus tripping the breaker in the vehicle. If that happens, you'll just have to turn off all/some of your lights to get your baseline load well under the 1500W limit.