Here is my example WIP. https://www.youtube.com/watch?v=yhXL_v_XKaQ  I'd say this is a hybrid but where models aren't hybrids, usually such animals as a horse, you should still be able setup the horse if you can assign the minimal amount of bones and not worry about the t-pose. The t-pose is just to ensure Human compatible animations and mocap but if you just want IK capability it should be fine but of course wont look right if you use Biped based animations.  I've done a lot of experiments, this is just a suggestion from my experience.

You can turn a CC3 character into a quadruped roughly through built in tools such as edit mesh and the morphs but I prefer using GoZ to gradually push the verts updating often etc, I've done this creating a mocap ready Bear.  I also have a tick like creature that I've modeled with Zbrush and used CC3 bones, duplicated the arms and hands many times. CC4 detects the CC3 bone naming convention and I have to use HIK characterization.   There are a lot of updates and maybe new features coming. I heard from a webinar last night (August 3rd)  there will be a big update in Sept which should make it easier to customize HIK characters and potentially add clothing to them.