Depends on the cheater. Did the cheater cheat because of an addiction to the act of being a cheater.
Or did the person just want the freedom to bang/love other people.
Person one, no... I don't think so, I think that person would benefit from being monogamous, with a dadt policy and label themselves a cheating fetishist. Thats the reality of what they want. If it was going to be remotely ethical.
The second person, sure. We see it happen here. I think there can be an allowance for confusion if someone is non-monogamist but brought up in monogamy. However... I would hazard a guess that most cheaters end up not being able to stay with the person they initially cheated with. That is a serious mind fuck and an emotional kick int he ass. Any spouse that can heal and put up with that is truly a strong individual... So while the "cheat" may be the gateway, I am not sure that the cheatee would end up being a good metamour