We talked awhile ago about being more creative with pedestal baskets and creating some man made hazards around some baskets a few years ago. These were some of the pictures people posted:
Just as an observation, one of the reasons Albert Oakland holds up better as a disc golf course today as opposed to White Birch are those gnarly cedar trees. They knock down a lot of shots and protect a lot of tees. Without them the old course at AO would be a hazard. Some nasty evergreens that will fill out around baskets can add a lot to a boring hole. You have to get them pretty big to begin with or the hackers will stomp them down (at least they did when I tried to plant them at White Birch) and the big ones ain't cheap.
OB areas out in the fairway are cool in theory. Basically narrow up the fairways in the 300' to 400' corridor so that when you are bombing away with a drive there is danger there. It's kinda the same concept as a sand trap only different. I'm not sure how you do that in a natural setting. Certainly you can do it with yellow rope and hay bales, but that is not realistic for an every-day set up. To me the gnarly evergreens you can't throw through that cut off your sight lines can do a similar thing as OB in that it punishes you for getting out of the fairway, it just does it in a natural way that will mix with park land better than artificial means. It kinda depends though, a lot of parks have a planting plan and will restrict what you can and can't plant.
Not that it's perfect, though. One of the problems with a course with no canopy like Sioux Passage is that big arms can spike hyzer up and over anything you put in front of them. It's more of a 100% penalty when you can make it an OB stroke. Course without water have a harder time doing that, and the County course other than Unger are short of water. There is some other landscaping you can do to create an OB line that looks OK in a natural setting, it all kinda depends on what the park wants to do. It's a lot easier to do things on a private course where you don't have to make it blend with the overall park.
I kinda like the idea of artificial island holes as well, and you can use landscaping to do that. A short ace-run kind of hole with a defined landing area and mandatory re-tee can shake things up. Most people hate that, though. I suggested that we build a rock wall around #9 at White Birch and make it an island hole, and pretty much 100% of the people I mentioned the idea to hated it. Of course making White Birch harder probably misses the point. Making Sioux Passage harder makes more sense.
To start out with the place I'd suggest trying stuff at is Creve Coeur. A pedestal hole or the like could help jazz up the flatness out there. Also if there are small trees planted at CC you won't have to worry about them getting mowed over.