I've edited my base character with extra bones to be dedicated and labeled "spring joints" I show the result of movement in the attached video by adding joints in key locations.


I further recommend you allow batch import of joints built into the character identified as "SpringJoint" with symmetry and hierarchy support (imports a spring joint chain) and either automatically creates a group from the parent or can be imported directly into a custom named spring joint group.

By default, I think CC3+ characters should have had extra joints for spring effects but at least now with AccuRig you could have a feature to let users add a "springjoint" so users can experiments and add them wherever they like.

Allowing users to rename non characterized joints with the name "springjoint" allows for easy recognition and batch importing - either that, allow spring joints to be used on any joint embedded with the avatar with the identifier "springjoint" as a name alias & target for spring joint function.

If specific joints are activated additionally as the alias "SpringJoint" then it keeps the Character light weight and perhaps additional joints can be created on export in the same location with the name (first child name)_SpringJoint_(R/L