Hi Steven. You know your round best mate.
For me a van mount would be almost impossible to operate from a lot of the time due to the layout of my round, parking etc. For me a trolley is by far the best option and it works well. So it could work. However, I have two friends who both work with their wives from van mounted systems and that works well for them. Both of them however, also have backpacks on board their vans as well for those awkward to access jobs. I have another friend who works with his son from a van and who both started with trollies, went over to van mounted and back to trollies again due to the nature of their work, parking probs and so forth.
I think, look at your round, see what you think will work and go for it. If it doesn't, learn from it and try something else. You'll get it down to a fine art in the end.