You know how the inflator tool in Garry's Mod works? How it basically makes a limb bigger or smaller on NPCs and ragdolls? I wonder if you could make/find a similar tool in this game and use it for all the body shapes.
You could use a tool like that to not only give a way to have a fat playermodel without needing patches for clothing mods, but you could also make emancipated models look thinner and the stronge models look strong, and all that while being able to have the fat/obese clothing built in as basically connected to the thickened/thinned limbs.