The spectral bandwidth of the pan only covers blue (just a little), green, yellow, red, red edge and NIR (just a little) MS bands. So the most you can pan sharpen would be 6 bands, but the common bands would be 4 bands b, g, r, nir. Compute pan sharpen weights for Gramm Schmidt would give you the weights tailored for his specific image. This method is only available at 10.1 and later.
You could sharpen b,g,y as one 3-band composite image and then ps r, re, nir for the 2nd 3-band composite, then combine them into one 6-band pansharpened image. You could even include the coastal and NIR2 unsharpened bands in this last composite image if you want all 8 bands. This would have to be done manually using the extract band/pansharpen function or suing the pan sharpen gp tool.