"I'm curious what magical combination of difficulty it is exactly that makes WM A3 such a Pipe Dream."

Let's consider that other Poser users were very keen to convert Sydney to weight mapping and gave up very soon afterward when it was discovered that her particular mesh was asymmetrical and a mess to correct.  I'm not saying that Aiko 3 falls under the same category, but someone would need to invest quite a bit of time with her in order to iron out any issues that may exist.  The Frankensteining technique always fascinated me; actually, a very long time ago someone posted a tutorial on the process, something I didn't pursue at the time.  I was quite impressed.