Meme, you are suggesting an arrangement that most people would shut you down if it was the other way around, ie. your OH earning more than you.
My OH and earn the same, however, he has very few outgoings (car/phone etc...) coming with his job, and he has no children, whereas I do and have many more outgoings. If the arrangement had been that I pay 50% of everything, he would have been left with much more disposable income than me. Considering I would have had to pay for 3 of us to go on holiday, I would have been left with having to go without on a lot of things whilst he was able to treat himself to everything he wanted. How is that supporting a healthy relationship?
Thankfully, he didn't see it like you and agreed immediately that the fair arrangement would be to start ensuring that we both ended up with the same disposable income. It still meant that he was better off as he didn't have to share with everyone, but at the same time, he paid 50% of the holidays.
As the years went, the arrangement flexed a bit, my income went up, his didn't, then he had to pay more tax, but I had more outgoings as kids got older etc... I think he does have more disposable income at the end of the month, but he pays everything to do with house repairs (even though we are now married so would be entitled to half), always pay when we go out so it probably works out fair. Last year I was short as we had to pay for our holiday and he paid it all.
He lost out big time financially by deciding to make his life with me and sometimes joke about it, but life is not just about money and as he's said million times, he is much happier poorer with me than he was with plenty of money on his own. Jointly, we are still doing very well.