I would totally enjoy having some super hung black guy screw my wife weekly. She deservess good hard sex once per week. She thinks she's fine but she hasn't had a good hard orgasm in years. Once she has one, she will want one all the time. I know her too well.
That should be a point of concern. It would be like getting her addicted to an addictive white substance ... once she's had it, and liked it, she'd want it regularly, but not necessarily at
your time or convenience. A lot of these type of arrangements go wrong when the husband realizes he's no longer in control; that his pleasure in observing, or even participating, are no longer guaranteed, and his wife simply seeks her pleasures when, where, and with whomever she chooses. Suddenly the cuck feels left out and even rejected, and then relationship troubles begin to brew.
So I would suggest you keep your finger on the pulse of progress as she develops, that she see this as a privilege you give her of enjoying other men, but that its conditional on your terms.
This whole idea of voluntary cuckolding should be used to pump UP the marriage, not threaten it.
Just my thought to this ... Mac