Personally, I'm not sure this is a great idea. The best analogy I can give is golf (which, in my case, resembles backpacking: moving a bag full of gear through the woods and high brush looking for an elusive little spot of white.)
I have a three-wheeled cart that will hold my clubs; it can be pushed or pulled. I can also carry my clubs, using a set of shoulder straps that are attached to it. I've found that I prefer putting the weight on my shoulders and dispensing with the cart. It just seems easier and less awkward to maneuver, somehow.
I suspect that a hiking trolley, in the woods, would be the same - especially since there doesn't appear to be any way to bend, which would make it difficult to maneuver around turns in the trail. Also, on narrow trails hanging on the side of a steep incline, if the wheel fell off the trail, it seems likely that it would drag you down with it.
Finally, the light loads most of us carry now would seem to make this somewhat irrelevant; it's just not that hard to carry the load.