again some times have passed, anyways i want to share some informations
Importing Collada meshes with rigging from Blender, DAZ, whatever into C4D works perfect.
The problem ist the C4D Collada exporter.
Even with the checked "export animations" checkbox all rigging information will lost (you can see by comparing file size)
So here is my little solution for this problem:
1) Export from C4D to Autodesk FBX -> all rigging information stays intact
2) Convert the fbx file with the free Autodesk FBX-Converter tool to Collada
3) Import into SL, checking the "include skin weight" and "Include joint positions" checkboxes (that are not greyed out now)
good thing aside, the converter fixes the different axes directions (standing Avatar in C4D -> standing avatar in SL)
keep an eye at the avatar scaling, it cannot corrected with Export/Import scaling (its in the rigging)
best suggestion, use real life sizes for your mesh in C4D (~180cm)