How to have Biped work with custom controlls ?

Hi,
I have a character which has to be used for MoCap animation. However, I need
that very same biped to have custom controls like splines for manual animations.


condition is the Custom controlls should not destroy the Biped's entity so that
it works as both for MoCap as well as custom animation under one Biped.

is this possible is any way ??? because my understanding is the moment i
put/link a spline with a biped bone biped's internal linking system gets
destroyed, and it become a normal bone setup.

plz help.
regards.