so far i found two solutions. 1. use the blueprint to adjust the scale, but it won’t affect too much, cuz it just simply change the scale, so if you wanna your character sexy or muscular, this solution won’t help. 2. use mesh morpher in the market, so far I found serval guys achieved morph by using that plugin,I didn’t try it,cuz its cost over 200 bucks in my region. (these two solutions are so far what I found, two of them could still keep the rig)
PS:I also tried to use my own mesh and remap the texture to achieve the seamless body change, but I failed, because the texture was already generated in metahuman server,I cant reallocate the map by using Wrap. nonetheless this solution is theoretical working, if you find a way to reallocate the map, try it! 