If you want to move your plants easily then I think rock wool is your best option.
There really is no need to have hydroton in the ebb/flow if you are using rock wool for the entire grow. In fact, I wouldn't want my roots to grow from the rock wool into the hydroton if I planed on moving them around in the tray.
I use a DIY ebb/flow that uses hydroton. But, I use individual containers.
If your not using individual containers and you want to move the plants around, then I think the rock wool is the way to go.