Ethernet FAs cannot be converted via symcli like FC FAs can, it must be done via bin change which will also include updating the Remote Machines Table (this must be done on both arrays).

Technically a direct connection may work but keep in mind that the Symm will create TCP connections from all local RE directors to all remote RE directors in an SRDF group and if you have two direct connect RE ports this would generate an error I believe. If you create an RDF group with just one RE in it that may prevent errors from ocurring, but then you would not have any redundancy or load balancing.

If you are not going to be using 10Gb iSCSI or FCoE in your infrastructure then I recommend you swap out those i/o modules for either 1Gb iSCSI so you can use your existing network infrastructure, or swap them out for FC i/o modules which support direct connect for RDF.