We would like to go to a continuum of state, instead of the discrete levels in the quantum situation. Hence, we need many different levels that are spaced closely to each other. This could be reached by having a nucleus with a very large spin I (and many m_z, preferably integer), having a small, nonzero eta so all levels are close to each other, and by having Q or V_zz small (e.g. a nucleus with a lot of neutrons and not that many protons).
However, I don’t think this is achievable in practice.