is there any way to configure a generic rig? and to mask it?

Hello! I have a group of generic rigs with exactly the same skeletons and I managed to import them in unity and make them work sharing the same animations (sort of retargeting, based on the fact that the animations are exported with exactly the same naming convention). Hurray!

Clearly, as expected, the different proportions of the characters created weird results in terms on animation, on some of them. I have observed the phenomenon (I have some skills in rigging in 3d), and I think that I can fix that problem somehow if only I could configure the avatars of those generic rigs or to mask them to make sure the wrong translations of the joins don't influence the proportions of the character.

So, my question is, is it possible to manually configure a generic rig? if it's possible, how can I do it?

Thanks!!