It would be possible to use my cloaked party robes for the clothing slot (B) and another mod for the robe slot (I) with some adjustments. If you find and replace all instances of modeli and texi with modelb and texb in the .ini files for my cloaked party robes, that will make the installer change which appearance slot it writes to. Then you should be able to install both mods normally.
I might consider adding that as a standalone option in a future release.