OP, It took me five years to find the right way to have the conversation you are describing and I think it also depends on the character of you and your wife, and the deal your marriage is built on.
The breakthrough for me was finding the right moment, the right tone and the right question. Our marriage had been almost completely sexless for five years - I tried everything. One evening when I was feeling chilled and teasing her gently about the lack of sex in our relationship I asked her, with warmth and without blame, that she could not think it was fair to me that there was no sex. She conceded that was not fair. We agreed to both think about it and continue the conversation.
What was important to my wife was
1) she trusted I was and would be honest
2) I promised not to do anything that would threaten the security of our family. My starting point that we both had a huge vested interest in making our marriage work - emotionally, financially but most importantly for the sake of our kids
3) We discussed and agreed a solution (we discussed an open marriage but I could not see it working), consider the cost of punting is a minute fraction of the cost of a divorce
4) Be discrete. I promised not to discuss the arrangement with anyone, particularly our family or friends, protecting her pride and not humiliating her either in public or private is VERY important - so find tactful ways of negotiating boundaries and "you" (i.e. Punting) time and keep your mouth shut.
5) We agreed to try it and see
6) We agreed it was not something we would have as an ongoing discussion - so I am not "rubbing her nose in it."
I suspect most wives are typically much more bothered by the deception and humiliation than they are about the sex.