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Stitching the bracketed exposures separately as three sets of four will not result in identical panos.
The control point detection system is very sensitive and will not necessarily find identical CPs at different exposures.
If you what to produce thre separate panos from your bracketed exposures - not sure why you would - then I think you probably need to use hard linked stacks and output by layers.
But perhaps I have misunderstood your question?
Nikon D40, Nikkor 10.5mm fisheye, Sigma 8mm f3.5 fisheye, Nikkor 18-55/50/35mm lenses, Nodal Ninja 5 Lite, Nodal Ninja 4 with R-D16, Agno's MrotatorTCS short.
Nikon P5100, CP5000, CP995, FC-E8, WC-E63,WC-E68, TC-E2, Kaidan Kiwi 995, Bophoto pano bracket, Agno's MrotatorA.
Merlin/Orion robotic pano head + Papywizard on Nokia 770/N800/N810 and Windows 8/XP/2K.