What I'm saying is you can leave the gold-plating intact. Apple has to service the unmodified part. So if the battery dies at 50% or the buckle fails, those have nothing to do with the gold-plating. If the screen stops responding or the digital crown stops spinning, then maybe it is the gold-plating but Apple still has to do the diagnosis and prove it.
Apple doesn't have to do anything. I think I can just about guarantee that if you have your watch taken apart and submerged in a chemical bath and gold plated, your warrantee is toast. I would think that this would be obvious to everyone.
By the way, I think it looks great gold plated, but don't kid yourself into thinking that your warrantee will still be in effect. It won't.