Yes, this is a solid analysis. In my view, people should assume the marriage will end, as one of the spouses has "died" and the vows were "till death do us part." That doesn't mean the survivors of that marriage (in MtF transition, the two women survivors) have to get a legal divorce, but they should have some kind of separation, to let themselves get to know each other all over again. The former-wife should not have to bear the full burden of supporting her husband through the surgeries -- she should be considered a close friend who may offer to do some of the support but will need other people to help too. After transition, the two people can make a decision about whether they want to "end the separation" and recommit to each other. A new ceremony seems like a good idea, even if it's only symbolic.
Pressuring the wife into supporting her husband through this terrible suffering because they're married and she owes it to him -- that just encourages her to act like her husband is still there, and all this talk about transition is just the husband's mental illness. The original marriage was between a man and a woman. If the man's not there anymore, neither is the marriage. Start fresh.