Include an option for communications over EtherCAT. This is almost always the best option for anyone that wants to communicate to/from a Beckhoff PLC, among others. Probably the best overall industrial communications protocol for real-time communications.
I assume that for that situation, the RMC would be an EtherCAT slave?
Yes, I would think in most cases as mentioned the RMC would be the slave. However, the Beckhoff machine (PC, CX, etc…) can be configured as either the master or a slave through the TwinCAT software.