Joint (mix) two figures , or add new geometry then add new bone for rigged figure?

kitakoredaz

Eg,, now I have one triax (or general) weight chain,. each part can roate free.
then I plan to add head part (eg edge, or crystal sphere) which can rotate with bone.

I can make head part as different figure (name it as head part) with one or two bone (if Ineed)

but there seems no way, easy connect the head part to chain1 as one rigged prop.
(I do not hope to parent head etc,, hope to make one rigged weapon by chain and head parts)

If there is no way to connect two figure,
Can I add another geometry , (imported mesh) to the figure, then just add new bone for new mesh,
and color the weight ?

about this case I can not use Geo grafting,, (there is no roop mesh which connect two parts)

I know we can easy add new bone, but about geometry, ds can not it still?

Or I must need to export chain and head part as one obj, then import the obj,
after that transfer weight and rigs from chain 1 by trnasfer utility,
then add bone for head part and color weight for the head part ?