How about some ai algorithm to identify the objects , possibly manually weighted with a physics imposter. Thinking something like the edges of a self organizing map. Or , something similar to facial feature mapping. Or maybe a 3d voronoi and some noise / smoothing for the paths. Or some flow field approach . I was thinking you have the map first and want to add roads later like in your pic.
But… Are u thinking to make the roads after the agent builds the settlement or while it’s doing it? I think if you want to do it while its working, the path finding algorithm will dictate . Does the entire simulation process need to be visually realistic ? Bc im thinking as the agent moves, if it builds and then deletes roads , thats not so realistic , but if just the end map is all that matters, you could just build/delete the road as it moves .
3rd approach i can think of would be to trace out the agents movement. Then when hes done, use his actual movement points to plot a line of best fit and have him build the road based on the line of best fit as the last step