Typically, SYSAM ties the license to eth0. Would the physical MAC for eth0 change?
Alternatively, you should be able to use a served model. In this case, you only need the eth0 MAC for the SYSAM server, not for each IQ node. This may get you around the issue.
Unrelated to licensing, but related here, MPX uses raw IP addresses by default. Make sure that you tie your nodes to the virtual names and virtual IP for each node so that you don't run into a situation where a node shuts down if the IP address changes.
Mark