Nah, doing that by any renounced casino company or even the least casino platform is very unethical, except such betting can be done between very close friends, it may not even be staked with money but just mere words, just my opinion.
Look, I know this is just your opinion but what do you mean by "doing that in a renounce casino is unethical"? Are you trying to blame the gamblers for staking their money on those type of games, or the casinos for supporting those game in the first place? Who's supposed to be blamed for doing something really unethical like you said?
The world is such a crazy place that people just wanna be good/bad version of themselves -- if the laws can't stop people from committing sinister crimes, do you think any bookmaker would agree to this? All about money!!
But the case where casino will integrate such option is not morally comprehensive.
Don't try to twist this whole thing... Say whatever you have to say and make it literal.