Judging by what you have said you want it for, I think a trolley system would be perfect for you. You can always use a trolley as a van-based system simply by putting a longer hose on. You cannot use a van mounted system as a trolley.
Go for flexibility
And a 100 psi pump will pump water to a height of about 200 feet. It's not the height that you need to worry about, it's the adjustability of the flow rate. That is down to the pump controller you choose.
As you are going to be doing fascia the finish you need won't be anything like as good as on a window, so you can probably get away with using less water for washing and much less for rinsing.
It's only a guess, but I'd imagine that 1 litre per min would be quite enough flow, so 50 litres will probably last almost an hour.