Just about all tripod heads rotate from the bottom section. However this means that it is not a good idea to alter this setting once you have levelled up, or you will need to level your NN again.
I often find it necessary to accurately set my starting point for rotation, to achieve the minimum number of shots, or to adjust where the seams will come especially in subjects with moving parts.
In days gone by it was easy to purchase rotating sub-bases. I think the time has come with Pano-photography, when such a part is again necessary.
I think that the rotating part on a ball head is in the wrong place... If it was on the top, it would rotate in a levelled plane. As it is it always revolves on a canted angle.
I do not use a head between the legs and the NN ... so I am unable to separately rotate anyway.... I know you can start anywhere between detents but then your end or important seams can end up anywhere.
Nick it would be good if you could think about making a thin lockable but adjustable rotator, that matches the NN range; either for use on top of a levelling head or directly on the legs.