It could accept a Sphere. But the idea for more than 2 years now was not to work on enhancing or changing EuDX but design a new tracking API that would replace EuDX. Unfortunately, we still don't have that apart from the work that Bago did.

I personally think that it would be nicer to have a sphere as an option. But it will brake backwards compatibility for a lot of people as EuDX has been around from the early days of Dipy.

I am happy with anything that the rest decide.