One Pipeline I found is downloading make human, make a male/female version. Import to 3d modeling program of choice (Blender, , maya) and touching it up a bit, adding morph targets to said characters, import those characters into the engine, and create a basic system that can adjust the morph targets accordingly with a slider. If you plan on doing this or having someone do this you will need to make the clothing the same size as the base model and morph the clothing accordingly, so you’ll need to have the clothing automatically load the morphing values depending on your characters size and load the values into the clothing of choice as well as have morphing set for each individual piece of clothing. Definitely worth effort if you have the patience though, it would be great for pumping out custom characters
Someone already managed a start at this and posted their creation for free use on the forums
https://forums.unrealengine/showthread.php?74688-FREE-Character-Creator