OpenRCT2 changed how it defines sprite groups which offers more flexibility. It now defines one combination of bank and roll (with some exceptions) which creator-defined rotation sprites. Rotations can be 0, 1, 2, 4, 8, 16, or 32. I believe it would be good for the tool to use this system at least under the hood. Some things that are made available by this method are diagonal versions of all the elements, which is performed by setting the appropriate groups to 8 rotation frames instead of 4, for example.