When I started wfp it was with Peter Fogwill's trolley which had two "slots". You could choose to take one or two 25L barrels with you thus giving 50L. It also had a small car battery and shurflo pump on board and probably weighed about 65kg all up.
I later dropped the battery and shurflo and got a backpack which by using a carjack and spreading the upper rails of the trolley I could drop into one of the spaces for the barrels. Weight about 50kg for carrying 45L water.
They were both a handful on a slope and especially on kerbs.
I can see uses for a 100+L set up say on the right streets where parking is tough or in pedestrian areas where you don't want hoses everywhere, where it is level - and of course you don't have to take a 100L every time.
I wouldn't want to use it on Lyme Regis (Broad Street)! Maybe Clovelly?