The microwave is out of the question, unless you happen to find a really small, low power one, but even then, you're still probably talking almost 600W of power.
The battery back-up and an inverter are valuable, and worth the investment (size it to your needs), but a Genset will be VERY valuable if you plan to use the RV.
But, you can use the RV like you would a tent, and not need any extras. Pretty much depends on the amount of "luxury" you are looking for.
Not sure why you don't want the water and holding tanks, or the head.....those are things that make the RV...recreational.:)