I bought a trolley system origially and then upgraded went along, and that bit was put together by myself, but the original was off the shelf.
It really depends on the depth of your pocket.
Were I starting all over I would go for a basic off the shelf system, whether that be van, trailer or trolley.
I would not go for any of the big boys toys, I'm a one man outfit, not a large company and I really don't think there is any point for someone as tiny as myself to lash out several grand for WFP.
If I was going for a van mount then I would be swinging between fully fitted and part DIY (I'd want to have a system whereby I could fit my own tank into the back of the van)
Were I a larger company I would be considering leasing from one of the big boys, tax effective and less initial outlay...
It really isn't as straightforward as you might think!
All i would really say is; "Get what you NEED, not what you WANT!"
Ian