"...or are you just re-shaping to fit another figure? WW2 which comes with P8 does that."

My figures are custom rigged and morphed.
I morph them in ZBrush, then adjust the rigging to match the new shape.
The grouping is still the same as V3/M3, but joint centers and falloff zones are completely different.
So none of the automated conversion tools would be any use anyway.

I wonder how similar Aiko 3 and Aiko 4 are ?
If they are shaped the same, converting clothing from A4 to A3 should just change the grouping, not re-shape the mesh, shouldn't it ?