Thank you for making these observations. I'm already running into some of the issues you mentioned... but also, much less than I anticipated.
Since I came clean on Tuesday, my wife and I have probably spent more time talking about relationship issues than we have in the previous 25 years combined. So even if the triad doesn't work out, my wife and I are both committed to improving communication.
My wife is obviously still very much hurt and in pain. But she insisted on meeting U as soon as possible. U is simply stunned that she still gets to see me, and she wants to meet my wife as well, so she agreed to the meeting. We met for dinner last night in Fort Worth.
Dinner went like this: The first five minutes everyone was awkward, then came 15 minutes of small talk, then about the time the food came out, all the feelings came pouring out. The two women talked nonstop for two hours. I think I may have said 10 words the whole time. By the end of dinner, the two were starting to be friends, and we even went for a horse-drawn carriage ride to continue the discussion. It was supposed to be about 20 minutes, but as I said, the women were discussing the situation, as budding friends now, and that carriage driver was getting an earful, and I think the carriage ride went about 45 minutes.
The particulars that came out of last night, in no particular order, are:
1) that while my wife is still very hurt by the lying, she was actually not bothered by the sex.
2) While my wife is not sure yet that she wants to remain in the relationship, she is intrigued by the suggested arrangement and agreed to give it a year before she made a final decision.
3) U is having difficulty grasping the concept of a romantic relationship involving more than a couple. She does not quite see this as a... triad? but more as two couples sharing the male. We are trying to get her to understand that while she and my wife may not have sex, they do need to develop emotional intimacy with each other.
3a) Neither woman is bi or is interested in sex with the other. But we spent considerable effort emphasizing to U that if this relationship is going to work, the two women would need to build trust and emotional intimacy. We had a difficult time convincing U that 'emotional intimacy' was not code for lesbian sex. She finally grasped the concept after a texting conversation with my wife this morning.
We have a lot of work cut out for us, but I'm encouraged by the progress so far.