Thanks for all the help everyone!
After much thought I have decided to go with the Major Transform (15cp/d6).
Healing (BODY) did run a close second, after all this is what the power does - restore BODY to a damaged item. But I had to consider, what the power is doing, and has the potential to do. It was not good enough just to consider how the power is used.
Minor (or cosmetic) Transform would really only make an item appear newer - cleaning the surface, enhancing colours, removing flaws, etc.
Whereas, the power as I have conceived it, allows for an item to be restored (albeit slowly) from only fragments.
This makes me ponder a few other questions about Powers and how they are used, for function is not necessarily and indication of potential. Keep an eye out for further posts regarding Powers: SFX vs Function and Funcion vs Use.