I recall seeing one similar in size and purpose that was entirely homemade about twenty years ago. If I remember correctly it was made by the owner of the golf course near Cloverdale where we were playing at the time. Didn't get the chance to talk with him, but one of the employees there pointed out some details.
It was entirely hydraulic drive with the engine just running the pump and hoses to each wheel driving them independently....true all-wheel drive, with the distribution of effort assured by size of fittings/hoses. She said the owner was quite a tinkerer and that the little "jeep" would pretty much climb any hill that the driver had the nerves to tackle. I think the engine was something like a 10-horse Briggs. Not made to throw great rooster-tails of dirt or "get air", just get where you want to go despite the conditions, and take some tools or some golf clubs along.
I remembered at the time having read about some early "dune buggy" type vehicles that used similar hydraulic drive systems very successfully, but I think the cost was prohibitive unless you had access to some salvaged aircraft or industrial pieces and some hydraulic expertise.
I've always been a very interested observer and fan of such DIY engineering and seeing how things like that get done, but haven't been a very prolific achiever of any major projects myself.