You know you can export and modify any asset you buy on the marketplace right?
if all you need to do is match an apron you don’t need anything. Delete or do not export LODs, load up in Blender. Load the model under it for sizing. Go to the sculpt tool and deform away to fit.
So long as you do not alter the verts at all - by removing or adding any - weight paint, morphs, and whatever else will still work.
Preventing clipping is more of a challenge. You would have to remove parts of your character that are under the clothing to prevent it.
in a pinch you can get the shader to move the vertex inward based on a texture and negative normal ws.
so when clothing A gets put on, Texture A is used by you skin shader, and you solved clipping.
Making the texture can be problematic- because everything is unwrapped differently. But its also just a texture. You could even generare it in engine with a RT system and save it - think Bruks impostors system, but for 1 character and 1 cloth item to produce an occluded geometry texture…
id make this, its just that like 2 people would buy it, and the rest would just paint textures…