Well, maybe you are Worrying about something that is not really that much of a concern. Whatever the case, talk to your wife to the point of exhaustion on this issue. Place some extremely severe limitations on such a situation, should you Both decide to take this step. I would ALWAYS err on the side of the marriage relationship !
No way I would ask my wife to do this if I thought I would lose her and I've said to her I do not mind giving her up for a night as long as she comes home with me. I get she might feel a certain way in bed with a black man but I am a good provider so I have that to offer. And my wife is not doing this under duress, she is genuinely interested in a black man as a sexual partner and that excites me. My wife does not do anything halfway so I know she wants this for herself.
Certainly understandable. There is a perspective of such a situation being viewed as 'a gift', from Husband to Wife. Still, such an undertaking must be approached with Extreme Caution. As an example, consider a "Worst Case Scenario" where at the very least, a minimum of 3 Lives are completely devastated ! Realistically the percentage of couples ( triples ) that can Manage this Situation must be below 1 %. I think this takes the complexities of Marriage to The 'N' th Degree. Definitely an extremely unique interpersonal inter-relational Situation. NOT to be executed without as complete an understanding, of ALL Possible Results ! Personally, I don't know that I would want to subject myself to such psycho-emotional Stress. Prayers for those attempting such ( "Better Man than I, Gunga Din" ) !!
We've had many talks about it in various settings like over dinner or during sex. We are a solid couple but I never in a million years would have thought we would be contemplating this in our marriage. Admittedly sex between us is not what it used to be so that might be one reason she wants to try this.