Of course, off-road buggies have been built for years ... it is important to build a safe and solid chassis. Think it's too much for you? It may well be, but never let that lack of knowledge ...

My other idea was more a question; could a buggy be built completely out of sheetmetal? Basically build a unibody or monocoque vehicle, but design it to work off road, and be made of thin ...

Up until recently, if you wanted a road-legal, tube-framed, rear-wheel-drive off-road buggy, you had but one ... provided you build it yourself Ikea-style and BYOM (Bring Your Own Miata).