Agree. Really the only solution would be to approach it the same way we would do any other bush map: a full photogrammetric or lidar plot, with fieldwork by a professional like Alex.
The bush on the Margaret River Maze map was very frustrating to do, and very poorly done, so the courses had to be set so that no-one would notice.
Alex is here soon doing Jumbuck Hill isn't he? Maybe he can pop in to Garvey Park in his spare time :-D
Fortunately the biggest chunk of bush on the map is revegetation with signs saying 'do not enter' so that shouldn't be too hard to map with OOB.