Coveting in the Bible is about property, land.
You just talking about being envious or jealous. It's not actual same thing people do to steal or buy or invade other people's land to take possession of it.
Sure you could steal someone's else's identity, or fake it. But you can't take someone's health, clone their fingerprints, take their talent and pass it off for you own, people will find you out.
Adultery is what happens if you covet someone elses' spouse. Their body does not belong to you. It only belongs to the spouse, if they are married.
You are confusing what is basically sensory deprivation, a form of neglect and abuse with coveting, and that is something else.
If you are married, and you consent to be apart and pray and fast, then thats ok. But if you are witholding affection from your own wife/husband, thats neglect, and even abuse. If you are wanting someone else's husband or wife, and have an affair with them hoping they'll be your wife or husband, you are coveting and stealing. They don't belong to you, its unlawful. It doesn't just apply to intimate relations but a heart matter.
So really if you can't handle celibacy, which is a gift, then you're better off married to someone who is NOT already married to someone else. Otherwise you'd just be fornicating with every Tom, Dick or Harry or soliciting prostitutes.