I'd like to generalize the question, especially with respect to the RM Mixers: Can one use AVB enabled devices, such as the RM mixers at least as stagebox on a per-channel basis? So for example: Can I choose input-channel 3, 4 and 5 of the StudioLive 32 to come from input-channels 1, 2 and 8 on the RM mixer, channels 1, 2 and 6 of the StudioLive 32 from the local inputs 12, 18 and 25 and route some the returns back to the RM mixer? Should be pretty standard today - almost every mixer on the market supports this.
Sure, I understand limited channel count due to limited DSP power, but swapping in remote ports for local ones should be possible. A 64 channel setup would be nice: The idea is to just remote control the RM mixers since they offer a 64 channel mixer. Again, there I would want to replace some of the inputs with the remote ones (this time coming from the StudioLive 32) for external sources positioned at the FoH.
And, by the way: I still think using a board as a mixer that actually mixes audio signals at the FoH position is not a good idea. Stop sending all the audio through the network and let the stagebox mix instead, like the RM mixers do. That way you do not need to worry about the long (maybe not redundant) network cable anymore, since the show will keep on running as long as the stagebox is alive. Much more intelligent concept. Then maybe provide an external DSP (place it on stage!) and you can expand your channel count almost infinitely and safe (limited by e.g. AVB) and provide emulations that need heavy computing power.