You can save the mapping of bones in your skeleton to the Avatar on disk as a “human template file” (extention *.ht), which can be reused by any characters that use this mapping. This is useful, for example, if your animators use a consistent layout and naming convention for all skeleton but Mecanim doesn’t know how to interpret it. You can then the .ht file for each model, so that manual remapping only needs to be done once.