Here's a harrow I built as a multifuntion tool. I can drop the harrow and insert a scarifier to trench. Later I plan to add mounts so I can add 4 more scarifiers for a chisel plow type tool. (This is an early pic as I've added a piece of steel to replace the 2x4!)
This harow works well after tilling to create valleys for seed. I've used it, laid out the seed, then went over the yard again to "rake" it in. Works fine.
Mine's not as complex as a TR3 type tool.