Logain,
Where did you get information that repeated ATG increases the risk of relapse, PNH, or MDS? Your choice to favor a transplant seems sound, but you want to make sure you've correctly assessed the tradeoffs.
Repeated ATG sometimes produces remission and sometimes doesn't. When it does, it can restore health temporarily or for the long-term. It's unfortunate that it takes guesswork to predict the outcome for each individual. Your wife's positive ATG response the previous time is a good sign, but you may dread another year or two of cyclosporin.
A transplant is riskier but offers the chance for a cure. I'm very glad to hear that a 10/10 match has been found. My wife had a successful unrelated-donor BMT after ATG, but her case differed because of her MDS diagnosis.
The "gotcha" is that if you're going to have a transplant, it's generally best to do it sooner rather than later. Sometimes the doctors try to get your counts up first, but at the same time they don't want you to have many more transfusions, or let more time elapse during which your counts might get worse or you might develop other health problems.
You didn't mention your wife's age or overall health status. Younger and healthier patients have the least transplant risk. Younger patients also have the longest lifetime ahead of them, so a cure is a clear goal, while seniors might favor a faster recovery and even short-term improvement.
Other choices include watch-and-wait, in case her condition improves on its own, growth factors to boost blood counts, or a drug trial. I assume that her hematologist is not recommending any of those.
You asked about relapsed patients who had a full recovery. One is
Andrea Pecor, who was one of the first patients to join Marrowforums, and is doing fine after 5 rounds of ATG, the last of them 14 years ago.