I think I did it on the advice... I made a mask, used a blur filter, and used the nvidia tool but the result turned out to be somehow strange (I converted dds to png, since the program does not see dds) p.s. in this part I am a noob...
A is by far the easiest, but may not be suitable if you need precise control over interior dimensions (ie: tile/grid based gameplay). You want this pivot to be as universal as possible so you can swap modular components on the fly, add pillars and trim pieces etc.