in the past, we also had to transfer some characters rigged with gear from softimage to maya.
keep in mind that mgear is generating extra joints for knees and ellbows wich si-gear does not have (maybe gear-mc has this extra bones?)
to transfer also the weighting from softimage, the joint count and names should be identical.
so renaming from _shd to _jnt is neccassary, but easy to do in maya…
so we ended up generating custom components (xsi-legs, xsi-arms) for mgear to match si-gear specs…
the workflow was with fbx export. in softimage we kept only the deformers (unparent it from the rig, no hirarchy), renamed it properly and deleted all the rig part, then exported to fbx with weighting and shapes…
this “clean” fbx is only for reference in maya rebuilding the guide and storing mesh, weighting and shapes.
in maya we rebuild the guide manually with the custom components and the fbx as a reference for placing the components, and exported the skinning from the softimage-fbx in maya with mgear export skin…(or alternatively with ngskintools)
when generating the rig and its controlls the naming should stay the same, so you can also export the animation as an fbx for only the controllers from softimage and merge it to the maya scene…(maybe some fcurve interpolation will not match exactly, but this should not be a big problem)
for the chicken guide from softimage, i think they used 3joint leg component for the legs…wich also exists in mgear (but with this extra joints on the knees…). but with ngskintools a remapping of joints is possible…
hope this helps