Ok, I didn't get it at first.  I thought it was just a pyramid with 4 sides, but I see what it is now, and understand why this was challenging.  I would have just used a feature called shape merge to create this.  It's a boolean operation that works using splines as the cutter.  My topology would be screwed up, but it would at least render ok.  I wouldn't try to unwrap it though.

Lux, I'm squinting to see the "artifacts" you speak of in your subdivided object, but can hardly notice them!  I'd consider that a huge success, and wouldn't care if there were some minor smoothing issues, because you wouldn't be able to smooth the boolean result AT ALL, unless you really cleaned it up.  That would be about as much work as just building it from scratch anyway, as you did there.

Great work, guys.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.