I actually have gone the opposite direction. I have a pretty extensive tool set that I keep at home and small subset that I keep in my field box. That way I always have the essentials I need when I go to the field and don't find myself discovering that I left my something on the bench when I get there (of course, that NEVER happened to me
).
The only things in my field box are:
A pair of folding hex-key sets (one SAE, one metric)
A screwdriver with multiple tips
A small adjustable wrench
A knife
Some tape
My battery charger (with assorted cables and adapters)
My LiPo Tester
A Pen and Notebook
Bug Spray and Sunblock