I think the perfect solution is an embedded chainer in nebula server, this way you don't have to do the round trip for each nebula instances, you can remotely process a nebula chain with only 1 round trip (not to mention network latency won't add on each instances).
But I imagine it is a lot of work ....
Reaper's native solution for remote processing (reamote) works this way : you choose a track you want to be processed remotely, then Reaper just send the original audio, and get in return the processed audio after the whole FX chain.
Gigabit ethernet old or not is still ample bandwith guys. 125 Mb/sec. That is pretty darn fast and can run about 250 channels of 24 bit 96 khz theoretically. Of course there is overhead to consider so numbers are far less but that is faster than any but the fastest spinning hdd can handle.
With link aggregation one can combine the bandwith of all your NICs and get up to 3 or 4 gigabits. That is 375 Mb/sec on my system. I am reinstalling my main computer and server to take advantage of this soon. I will report back once ut is up and running. Perhaps next week sometime.
Main comp and servers are dual cpu intel xeon workstations so these are no slouches. If there is a problem running this setup and we get low numbers, it won't be because of bandwith.