When thinking a bit more on this maybe nothing is needed other than different port offsets?
Yes, you can create multiple clusters using the standalone configuration by specifying distinct multicast address/port. The port-offset does not apply to the multicast port, only the normal socket-binding port (typically you would want each server in a group to use distinct service ports, but the same multicast address/port).
By default, WF uses "ee" as the cluster name. You can change this to any name you wish. This is configured via the jgroups subsystem.
Out of curiosity, which element defines the cluster name in jgroups (I looked in jgroups-as-jgroups_2_0.xsd and did not see any obvious candidate)