Rigify - Nondisruptive re-rig - How?


So i have a character mesh that is rigged with rigify that i want to change, i need to change the arms length so just a shape key will not do, i need to change also the rig it self.

Anyways, how can i change the mesh and then the rig it self to accommodate the changes with out losing all the shape keys and the drivers?.. i read that rigify has a “Nondisruptive re-rig” feature but i don´t know how to use it.

Thanks in advance for any information.

Not very clear understand question, but…
I hear, that we can modify meta-rig and re-generate main rig. Maybe it helps you.