We've done this exact exchange before where I say I don't appreciate you implying in a reply to my post that I'm childish or too easily scandalized for not wanting nudity in cas, seriously, cut it out. I use default bodies and skins so "nudity in cas" is very much not undetailed barbie dolls for me and I'd like to occasionally play during my lunch break, I'm not clutching at pearls here.
What you described is actually exactly how the ww streamer mode solution I tried earlier works, it didn't help. I think the tan lines are based on the alpha(transparent) channel of the clothings texture, not the shadow or specular but I could mess with it once I can get home and use s4s. I think I saw someone from the original archived thread is working on a full mod to deal with this actually (by resetting the bathing outfit every time it's equipped) on their patreon earlier but I'd need to double check