TECHNICALLY ... If da man steps out, sees da hot babe, tips her over, and gets united (sleeping has very little to do with it -- I've slept with whole congregations full of women AT ONCE! Really boring sermons, ya know! :lol: ) ...
1) He has STARTED the 3-step marriage process: Betrothal, Wedding, Consummation. However, he has started it at the wrong end, and in so doing, has OBLIGATED himself to complete it, whereas if he had started at the other end, there would have been opportunity to back out.
This 3-step process appears to be nearly identical to the modern process of purchasing real estate: Offer, Closing, and Occupancy. What the Bible says is that if you start the process by moving into the "for sale" property, you are obligated to perform the other two steps, paying Fair Market Value (established in Scripture). Interestingly enough, there is opportunity for the other party (the woman's / seller's) to back out, but not the buyer's (the man.) He's responsible!
2) The Bible NOWHERE says that his existing wives must be ok with this. They may well throw a hissy fit. They DO have to accept the fact that he HAS DONE this. It is done. It is unchosen reality that must be dealt with, as much as if he comes home and announces that he has terminal cancer or has lost his job.
However, it isn't ideal or the honorable way to begin a new marriage. More honorable than a one night stand, to be sure. But still a matter of playing catch-up with no bragging rights!
His existing wife or wives might well conclude that the Bimbo also qualifies for another name beginning with 'B'. They may refuse to share the house with her if she makes homelife a misery, such that he has to provide her with separate living quarters. None of that stuff is commanded, so far as existing wives thinking that it is ok for him to act like an alley cat in heat.
Having said that, there is a 180 degree difference between a wife saying, "You are the priest of this home. Since I submit to you as unto Jesus, I expect you to consciously attempt to act as honorably as He does. That especially includes the way you obtain and add a new wife to this family." vs saying "I don't care what the Bible says. I'm not ok with you adding another wife, and will fight it openly or subtly, tooth and toenail. It's only happening over my dead body, or I'll make you wish YOU were dead!"
In other words ... You may have to submit, ultimately. But it doesn't mandate your silence first. You still have a right to express yourself. However, a point will be reached where it is time to stop expressing angst, and start making it work, whether he follows a "most honorable" path or not. Bear in mind that if he screws up, apologizes, and does his best to make it right, God not only forgives him but forgets the wrong. The devil, on the other hand, will be throwing it in his face every chance he gets. Which side do you want to associate yourself with?
The same, of course, applies to us fellas when our wives lose it, then apologize and try to change. Got to decide which side we're going to associate ourselves with... In fact, it's best to do that BEFORE allowing Testosterone Poisoning to send us indiscriminately rooting through the ruffles!