Fantastic work lightborne, i tip my hat to you in the detail you have achieved. I did not realise you intended to release it, it must be a beast so your idea of two flavours is good.
Eden, i dont think you need it per say, LW out of the box renderer is good, just finiky to get good results if you were used to 2015 or before.
Third party renderers are hardly a new thing to even high end 3d apps. You could argue why people are spending vast sums of money on Maya or Max and then relying on VRay or some other 3rd party.
I find Octane good for some uses and native to be good for other. I cant of course speak for C4D.