I understand the theory of what you're saying completely, it's not that it's complicated.  It's that you know where you want these maps to go from zero to one (in grayscale) and the texture artist does not.  The texture artist has the technique to paint the maps and you do not (you said it yourself).  Getting those two sets of information coordinated into a finished product will either be slow, or expensive, or bad (unless you're really, really lucky),

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