Hi Spacewig,
Thanks for the question.
I’m not familiar with the Mackie C4 device, but if this device supports the standard Mackie Control protocol/mode like the MCU, then you should be able to make use of the Remote Control Editor. In that case, you would need to make Nuendo/Cubase sees your device as “Mackie Control” device, I guess. So, you just need to check the manual or the related forum if C4 supports that mode.
Btw, I’m not sure what you mean by “RME”. Anyway, hope that this info helps.