Currently, exports on server side are associated with a nodemap, thanks to a call to nodemap_add_member at peer connect time (.o_connect or o_reconnect). This is done for MDS and OSS servers, as nodemaps are primarily designed for identity mapping and user access control.
But the MGS could also leverage the nodemap feature, and implement access control based on nodemap properties. For this to work, exports on MGS side need to be associated with nodemaps.