An experimental Geometry Node rig system. This is not practical, just a test to see if it is possible.
This does not use a regular armature object.
The 'GN Rig Phyisics' modifier creates bone instances from mesh lines with an assigned Root vertex group.
The 'GN Armature Deform' modifier deforms a mesh based on the GN Rig object.
Bone weights are automatically generated due to limitations.