DST has been useing a multivalued RDN in EndEntity certificates for a number of PKIs and since 1999 when we started issuing certificates. We only do this for End Entities not servers. Basically the certificate SubDN looks like the following.
0.9.2342.19200300.100.1.1 = D01E473E000000F58FE3DDDC00000709,E = rweiser@xxxxxxxxxxxx, CN = Russel F Weiser,O = TrustID personal certificate,C = US