Softimage provides a development kit that allow you to create a customized character rig based on the default ones provided. The development kit not only lets you automate the choices you have for the attributes you want for your rig, such as whether to use a quaternion spine or not, but allows you to customize the rig completely to suit your needs.
The SDK is object-oriented, which means that you concentrate on building the components of the rig (torso, belly, arm, hand, spine, hip, tail, leg, dog leg, and foot) without worrying about many of the rig's implementation details. Moreover, you can mix and match each component as you like—create a two-headed monster, an eight-armed octopus, a multi-legged centipede, or any creature your production demands.
Also, because the rig creation process is scriptable, it's easier to produce large numbers of rigged characters that suit your production needs exactly and in a predictable manner.
For detailed information about the behavior of the each of the components of the rigs, see Character Rigging in the Softimage User's Guide.
For detailed information about the commands available to build rigs, see the Commands and Scripting Reference.