Sorry, Rocked, but I'm with everyone else. No contact and FULL transparency, or it will never work.
If you do this, the OW may react in an unstable manner.
Then again, she may NOT, and she may ALSO behave in that same unstable manner even if your husband begins to LIMIT his contact with her, or -- as someone else said above -- if and when he finally does cut off all contact, and then what have you gained? You'd just have lost several months of potential healing and restoration for your marriage.
Being the weather geek for our baseball league, they picked me to make the weather calls of whether or not to cancel games, umpires, etc. In Florida, with our "afternoon pop-up thunderstorms," that can be difficult. I made a decision early on never to cancel the games based on a FORECAST (what MIGHT happen), but rather by what the situation is on the ground at the moment.
I think it works pretty well in Life, too.
In 5 years of doing this, and studying hundreds (thousands?) of cases, and being personally involved in a dozen or so, I have YET to see one where the betrayed spouse regretted being TOO strict with their boundaries, especially as it relates to no-contact and transparency. Those that have regrets about being too LENIENT, however, are legion.