Whether or not is is supported, it is not recommended. The mapped drive will have to be set up for all accounts having to do with the Enterprise GIS and referenced the same in all aspects of the system. Mapped drives can be set up through Group Policy, but if anything goes wrong with that process the software will lose that connection and anything dependent on the files on the mapped drive will stop working. It would be much better to reference the UNC path, provided that they do not change. I wasn't able to find anything in the documentation regarding mapped drives other than something about Notebook Server but that seems to be a very specific use case.
