On PC, bodies are much more editable outside of 3D editing than they have ever been. Check this thread for reference:
viewtopic.php?f=237&t=104167 Just keep in mind that modifying many of those entries won't generate any changes.
Being more specific to what you asked, to change body length, shoulder width and arm length, the values you need to alter are after "spine2.ty", "right/leftArm.ty" and "right/leftHand.ty" respectively. And yes, I didn't mess up on arm/hand there. Additionally, one can modify neck length through the "head.ty" entry or just scale all these body parts together through "right/leftToeBase.ty".
It's also possible to change how the jersey and accessories fit through the THIN/THICK values. As for the "CAP" entries at the bottom of most players' appearance files, none of them have any effect.
How thick body parts are, however, is only editable outside of blender for players that use the default body model. These are the players that only have basic appearance information by default(only 11 appearance entries). For those players, most of which are retired, adding forearm, upperarm, trap, chest, abs, shoulder, hips, thigh or calf entries will change both the model and the accessories or jersey. An example: