How indeed do you tell your wife you like trans-girls and that she needs to be ok with you acting on it from time to time? I could only find one angle to look at it.
I think most of my readers- men, women and trans alike- would agree that there is no relationship without sex. A relationship without sex is called friendship- or family lol. I scoff and look away when people try to prove me wrong, as you would have to be severely misguided to try to prove otherwise. Similarly, a relationship can rarely survive if sex stops at some point. So, sex is a relationship starter, and lack of it is a relationship ender. Clearly, sex is the fuel that keeps the whole relationship engine purring. However, can a modern relationship truly survive the fullest extent of human sexuality? Can it survive the drive to do it over and over again in as many new and exciting ways as you can think of? Here, I am referring specifically to married couples. Can a married couple really survive her dying to try an interracial threesome, or him wanting to try sex with a cute trans-girl? Can it even survive something basic like her wanting to finger him while she goes down on him, or him wanting to try anal with her? It can get pretty ugly if these things don't happen when we want them to. We're talking cheating, costly divorces, and all other sorts of scandals.
So instead of wondering what the wife would think about you wanting to be with a trans-girl, you may choose to wonder what it is about total sexual fulfillment that is so damn incompatible with marriage? What angle should you assume in order to get down to the root of the problem? My suggestion is to look at the whole thing from a "what's the big deal" angle.
When you think about it, marriage has nothing to do with sex most of the time. It has a lot to do with lovemaking, and an occasional screw just for the raw passionate fun of it. The problem, I think, is that in marriage there's too much lovemaking and too little screwing. Most of us come from cultures that suppresses screwing and totally control it for the benefit of those who are happy to see you under control while they screw all the time. This is especially noticeable in the world's remaining dictatorships such as that in North Korea. People used to not want you to screw because it couldn't be monitored, measured and utilized in some way. But, we are at a point now where we realize we need it, and need it bad. We will not be sexually fulfilled in any relationship- marriage included- unless we keep lovemaking at the same level but seriously increase screwing ;) Oh, and knowing what the difference is and making sure your spouse does too is important.
If both of you understand this difference, then it won't be difficult to keep the marriage going and be completely sexually fulfilled. In this scenario, if you want a trans-girl now and then, your wife won't become this territorial bloodhound overreacting to everything, sick with worry that she'll have to leave the house you and her got together and go live in a tiny apartment at her age. ;)
Think about it, don't overdo it, be confident and see how it goes. I hope I have offered a fresh perspective that you can use to inform your next step towards a new, exciting chapter of your relationship. It could end up being wholly rejuvenating- for yourself and your significant other.