problems with a blouse, the body swallows parts of the mesh.

That's because the clothing mesh is clipping with th body mesh . Have you removed all body parts of the mesh that isn't visible?

Another solution works for me(works in all blenders versions) :

Go to sculpt mode mode from edit mode. Set the brush strenght to 0.150 and set the brush size to whatever you prefer. Go to the clipping part ot your clothing and paint over it. You might notice that the clothing part becomes visible. Once your done. Go to your layers and press shift to select both layers. Go back to Object mode and press join.

Save the whole mesh and check it out in Sims 4 studio ^-^.