Spousal maintenance isn’t usually decided on the fact that the mother has the children more since the split as more often than not the mother is the resident parent anyway and that’s what child maintenance is for. As you said, in this case it isn’t relevant. It’s normally decided when looking at the marriage as a whole who benefited the most financially and how much the other person had to sacrifice in order for the one who earned the most to get there and stay there. There has to be a significant disparity in both income and opportunity in order for it to be awarded so if as you say the circumstances aren’t so it wouldn’t even be considered.
He may have had a successful career before he married her but the crux of the matter will be how much his career would have suffered and not been as prosperous if she hadn’t been the one to continue to do the majority
of the care of his children for years in order for him to continue to be successful at the level that he was or is. Having children is an enormous decision because it naturally takes a lot of time, resources and career sacrifice in order to raise them. He chose to have children with her knowing this. The contract of marriage is there also to protect her being the most vulnerable party. The argument will be that her career opportunities and years of experience needed to get into any form of meaningful career now would have had to have been depleted for over a significant period of time after the children came along and that will have damaged her career options going forwards for the rest of her life. In that time he’s continued to have the ability to not only earn a high wage but gain the years of experience and valuable skills in order to get him where he is today. That’s what he is paying for. She can’t financially support herself adequately to the standard she and more importantly her children have been accustomed to because of it and the children will suffer when he can comfortably pay to avoid it.
The fact she works part time and doesn’t earn anywhere near as much isn’t relevant now either. The argument will be made that if she had the same opportunities that he had then she may have had a stable income to support herself now and wouldn’t need spousal support.
The fact he paid all the mortgage whilst may on the surface seem unfair, is also not hugely relevant. She cared for his children so he could earn the money to pay the bills without it any affect on his career. When the children were ill, she would have been the one to take care of them. When the children had medical or school related appointments she would have taken them or been there for them. When the children had hobbies or clubs or social opportunities that fell during her husbands working hours she would have been the one to take them so it had no affect on his business or career. Here is his financial gain. If he had to cut his hours and working days short to provide equal care he wouldn’t have had as much success with his business and earn what he does now. Why shouldn’t she have her wages to herself if they’re a fraction of what he was earning and she was doing the majority of the care and not able to work and earn full time.
He signed his marriage contract knowing that half of his assets would belong to her so he was clearly happy to do so. It’s entirely fair for him to have to pay for his past career stability at her potential expense when she now has nowhere near the career or earning potential she would have if she had worked for those ten years or so but she now has no financial security now that she’s being divorced.