Why, that's very easy. Just dial the "Aiko" body morphs to get the body right, then go to the different leg parts and dial the local "Aiko" morphs back till you like the result. A full body morph is actually a sum of individual body part morphs, which can obviously be individually dialed. The dial in "Body" is just a master dial affecting all other dials with the same name. I don't remember (and have no Poser at hand) but those individual body part morphs might be hidden to reduce clutter; I don't think so, but even if they are, just get the free tools from Dimension3D which (among others) allow to hide/unhide specific morph dials.

This "individual body part adjustment" is fast, very easy to do, and works (I've been using it since ever, though with other V4 morphs).

There is a caveat in your case though: Since the "Aiko" morph radically changes the body shape, if you dial back the legs to vanilla V4, they probably won't fit anymore... Means you'll certainly have nasty bulges or ridges at the transition between Aiko and V4, because of the different body shapes. You might try to alleviate this by adding other morphs to the legs, or using the morphbrush, but chances are it won't be a one-click solution. You might have to settle for some Aiko in the legs, or less Aiko in the hip, or some such. Try it, you'll see.