Unity actually imports C4D, Blender and Maya files as assets. They get converted into FBX on load.
Would love to talk to you about this. A few years back we did a series of children's apps called Bramble Berry Tales. We're currently relaunching them, and did some exploration for how to create a multi-channel pipeline using Unity. Unreal is a little more AAA gaming, and we wanted something flexible. Unity was also a little further ahead in terms of realtime editing at that point, and the rendering for our needs (DOF, AO, skylights, AA) was kind of a wash. Our main goal has been to be able to produce apps, shorts, and broadcast content using a single pipeline. I found Blender and Maya far more predictable in terms of asset exchange, but people do it in C4D.
Non linear animation and use of mocap are really good in both Unity and Unreal. I started out as an oldschool, multi-plane camera, draw-it-yourself character animator, and applying those principles to realtime production make a ton of sense to me.
https://drive.google.com/file/d/1UtS7cucwZbPUBTP1-PcJ5BVFJfMGT1uU/view?usp=sharing
This is one of our early tests, straight out of Unity. Ultimately we didn't go that route because our first launch is for ipad - it's hard to control the experience that way, because there is too much variability in devices, and kids get the hand-me-downs. I think a hybrid approach can also work - build an animation bank, and output to game engines and render/composite depending on the best use in each case.
No matter what, would love to see what you're up to and share more of what we're doing.