Excellent work, thanks for your efforts.
For me that slope is far too steep (even if in a less slippery state) for someone who was having difficulty staying on their feet, or alternatively carrying approx 9/10 stones of weight, to climb easily within the time scales given, particularly when thinking of what else needed to happen. (Sorry I'm aware how awful that sounds, I'm trying to stay factual)
This being the quickest route and via the boat house taking longer this doesn't for me deal with any of the timing issues in fact makes it seem less possible.