Não, você não pode compartilhar novamente as montagens do NFS.
The short answer: it is not possible.
For at least nine years now, the Linux kernel has contained code to guarantee that directories which are NFS exported are "physically" present on the host providing the NFS service. "physically" present can mean that the disk is present via iSCSI or fibre channel or any number of other network layers, but that's at the block level, not the file system level. The kernel will refuse to export an NFS mounted directory.
About 14 years ago, the user-space NFS server implementation did allow this, but I only used it for a weird one-off situation for a couple days (definitely non-production).
I can imagine a number of use-cases where re-exporting an NFS mounted directory would be appropriate (I have a wild imagination), but it won't be easy to get it to work. Specifically, it appears that in recent kernels, fuse file systems may be NFS exported (http://lwn.net/Articles/281793/), so you may be able to put a fuse layer between the NFS mounted directory and the export. If you succeed, I'd love to hear about it.