I can understand about the render times. Some of my animations have taken half a day to render for a just a 30 second HD setup. Some apps network renderers only run on a local intranet anyway. Meaning that you would have to have the hardware (multiple computers) to make it worth using. Modo has an unlimited rendering client where how ever many computers you have you could run them each as a render node. I think probably what you are wanting though is where machines across the net could be used as a render node, much like the SETI program operates. I think some people talked about sending files to a Render Farm before, but pretty much none that I know of offer native C3d file rendering.
You can see some of my animations here:
https://vimeo.com/stage5 Nothing that will win an award, but they're all for the company I work for. So I never had tight deadlines on rendering them. One other thing that’s no fun is to screw something up in the animation and not realize it until after spending 12 hours rendering the whole thing. I think anyone doing animation in any 3d app has run into that before though.
I can't remember fully, but I vaguely remember Martin giving a reason for not proceeding with a network rendering option. It would have been a while back though. So, I don't think it would hurt to put in another request in the wish list since it's been so long.
One problem I've run in to moving my files from C3d to another app is the materials usually get totally chewed up and then I either have to fix them or recreate them anyway. UV mapped and diffuse materials seem to do relatively well, but procedural materials won't come across at all.
There are some 3rd party stand alone renderers, but the majority of them use Nvidia's CUDA (Octane, Corona, Red Shift). Possibly when Apple's Metal2 is farther along, there will be more options for stock AMD GPU's that Apple uses. GPU rendering can be multiple times faster than CPU rendering, but it does take dedicated hardware/software. You'd also be back in the same boat of moving your file from C3d to the rendering app. Most of which have their own material systems also. What would be better would be some type of rendering/material plugin bridge to another renderer, but I'm not sure how keen Martin would be to add that type of option either.
I understand your frustration, but it's one of the things we have to work around for now.
If you were on a tight deadline, you could possibly post on here and see if you could split up your animations and have different people render partials for you and then you could piece them together after. It would be nice to actually have a section of the forum devoted to "jobs" like this. Which might also be an alternate solution.
I have a MacPro5,1 that I upgraded with a GTX 1080 FE 8GB and also dual X5690 Xeon's. During the week while at work, I'm not using it. So I could help render some of what you need if you get into a time crunch.