I have that figure as well and she started giving me ideas that I still use today for multi-armed figures. You'll want to clean her up tho as she's 3 full figures that are all un modified copies of the main body, meaning there's tons of geometries that are set to invisible and chock full of morphs, some that aren't even being used.
But yes, I was upset when I found the tail didn't do anything! I DO have a naga lower half figure that is for Aiko 3 that was free as well, she's on this page
http://www.infinitedreamers.co.uk/2009/10/09/aiko-3-part-one/
For adding additional arms, I streamlined the process does take a good amount of work, but I believe it helps
Poser on it's workload. Rather than make a copy of the figure, make a plain, base figure and load morphs that affect the look of the arm, hands and collars ONLY. Once you have the morphs done, make a plain low prim primitive object like a box or even a single plain prim for each body part that won't be shown and place those in the spaces the body parts occupy. I find it helps the next step to name each prim the name of the body part cause your next step is to replace each of those body parts with the prims you just made. Then after that, make each prim invible and you should have your arms left! It'll still move and pose as a normal figure would, but with less prims to calculate, I believe. Cause most graphics programs still do computations and calculations and such for meshes, even if it's not visible.