What's causing the scrapes now in a bare tank?
You will always run a risk when adding anything. However, like you I agree with the more natural habitat to allow them to behave more instinctually.
Whatever you add make sure it is free of sharp edges jutting points etc. I also always make sure that the fish have ample room to swim around and under etc. leave room between the tank walls and decor so they can freely navigate. The tight spots is where you will find the most issue as they try to swim through or around and get hurt.