I don’t think it’s possible in Lightroom. You could, however, cut down the processing passes by stitching three bracketed sets first, and then doing the HDR/exposure fusion of the panoramas, so instead of exposure-merging eight sets of images and then stitching, you stitch three sets of eight images, and then exposure merge three panos.
It is possible to stich and HDR/exposure fuse at the same time in PTGui or Hugin which are packages specifically made for panorama stitching. I’ve created 360×180 exposure-fused equirectangulars from bracketed sets of images in both packages. You simply have to specify the bracketed groups before doing alignment and stitching, and you typically have your choice to either create HDR files, or use exposure fusing (e.g., enfuse) instead.