Poser 11 comes with a number of grafting tools:

• A classic one: 'replace body part with prop'. Before applying the replacement, clone the figure and switch the original on which you will be changing a body part to Poser Tradititional skinning. Then apply the replacement. After replacement copy the morphs and the joint zones back from the clone so they are defined in prop that now replaces the body part. You can then switch back to unimesh skinning if you want. Note there is no geometric 'welding'so keep a good overlap between the replacing prop and the remaining body.
• 'Combine figures'. see the manual. (This function is at the moment not yet available in Poser 12)
• Fitting Room. Cast your figure as a prop (my fig-to-prop script may help here) and, use the grouping tool to delete the parts of the body parts you no longer want, add the items you want to add, morph-brush to align, and export as one geometry to .obj. Then reload and make a figure out of the prop in the fitting room or the setup room.

Note that Poser Traditional Skinning for grafting work, replacing body parta and such offers the best options. The body parts are separate entities with separate geometry definitions so you can swap geometry of one of them without affecting the rest. Unimesh is a lot less flexible in this sense. Aslo traditional Poser bending, with zones so bending weight for a vertex is defined by xyz positoin is more open to grafting than weightmapping is. That's why when using 'replace body part by prop' you have to do a 'copy joint zones'. With the loss of the old body part the bending info was gone also and needs to be restored.