Hi pacificm,
Thanks for the suggestion.
Going by the simplicity the Maximo workflow has to be imported to Cinema 4D, I assume this simplicity should determine the level of complexity (or lack thereof) for the facial animation. I would exclude Joints here for this, as they would require a complete new weighting and creates a lot of considerations for the otherwise, as mentioned, simple Mixamo workflow.
I would think the most versatile technique would be the Pose Morph option.
I recorded a quick clip for you. This was done in just one minute. There are lots of options in the PoseMorph Tag.
https://www.amazon.com/clouddrive/share/rS2Mp5wKEgZpJz02KZrThqfpI05nvdDfKYGFPjaJWho
In an older version this was explored here:
https://www.cineversity.com/vidplaylist/introduction_to_cinema_4d_r10_bodypaint_3d_r3_series/butterfly_rigging_and_morphs_part_1
… as well in part two.
The Driver tool would be to name as well, here in conjunction with the Pose Morph
https://www.cineversity.com/vidplaytut/creating_a_cartoon_character_in_cineversity_brand_id_mouth_control_rig
Does this come close to what you are after?
Cheers