She has no job persperctive anymore since not employable anymore because “she did not work” while she took care of kids and household for 20 years. In the mean time, she could have created her own nail studio and have a much better life than with marrying you.
Anyway a lot of coulds/maybe.
If you want to have that discussion with her, you have to be able to see stuff from her perspective. Otherwise you will hit a wall.
Wait until you have kids and take care of them for one week all by yourself and you’ll definitely change this number upwards 
To be honest, from what you are describing and discussing here, it doesn’t sound to me like you are ready for marriage.
I earn around 3 times more than my wife does and also pay more than 75% of our joint expenses. But in the end, it’s only money. Love and relationships are important to me, money is only so important as it covers my basic needs for food and shelter. There’s no amount of money that can outweigh the love my wife gives me everyday and the love and care for our daughter. Maybe I’m all by myself with this opinion, but for me it’s either all in or nothing.
She already has her own nail studio since 2019. She already earns more than she would as an employed person (this job is paid rather poorly, 3.5k/month). There is no room to expand the business as there are already 100 other nail studios in Basel. And she doesn’t even want that. She is happy with her one-woman business and what she earns right now. Thus she maximized her income and has literally no potential left for a higher income.
How about this:
We go for a marriage contract with the Gütertrennung. So no splitting 50/50 in case of a divorce, everybody just gets his assets. Of course that wouldn‘t apply to the property (we‘re listed as 1/2 owners) and 1st/2nd pillar as there would still be a 50/50 split. We have a joint account for all shared expenses (house, food, kids, vacation, taxes etc.). Plus both have their individual accounts. I‘ll transfer her the amount what she lacks to earn 60k. Lets assume she earns 20k and gets 40k per year from me. We still split the joint costs like we already do now (% of total income).
If we split, everybody gets what he/she deserves?
Turns out it’s not even a question for her as she wouldn’t want that. Either we’re both all in or not, no room for discussion. But is that really fair in my situation?
Biggest question is why is that … of course if you love each other it may sound like you don’t trust each other any more and make it not that sexy …but if she absolutely does not want it … well … maybe she already has some second toughts
The problem is not really during marriage. The problem is after divorce. If she reduces work to look after children, her economic prospects are hampered (as would be yours, if you did instead).
The only easy fair solution would be to splitt child raising duties equally and everybody keeps their own economic proceeds.
That isn’t economically sensible as you earn much more. But to fairly push raising the children to her to earn more money in total, you need to compensate her even after marriage. For the continued opportunity cost of having raised children instead of developing economic prospects. (And also a share in your opportunity to develop even more)
A good question is always: Would you take this deal if the conditions/positions were reversed?
If she would earn 2-3x more than me? Absolutely. Why should I get money that I wasn‘t able to amass in the first place?
If you choose to reduce working time to raise your kids while your spouse works the swiss law enforces an alimony to cover your expenses after divorce. So you are anyway covered.
You would tank your career to raise children and expect nothing in return? Somehow I don’t believe you.
No. What I would expect in return is to get the amount which I would have if I didn‘t do that. Why should I make a profit on a marriage? Why should I boost my net worth that way? Wouldn‘t be fair?
Lets say if we don‘t get married and don‘t have kids, we amass a 4 million net worth by the time we retire. 3 million by me, 1 million by her. Should I gift her 1 million if we decide to split?
In my opinion yes. She was your partner for X years, worked 30% to take of your kids, and gave you the peace of mind so you can go to your high paying job without thinking what happens at home, or dating real gold diggers. Note that the opposite is true, you may decide to “lean fire” in 3 years, for some X reason, then she would support with income.
If you are not OK with this with it maybe do not get married? you can always stay as a non married couple with kids.
Nothing else I said. But it extends past marriage.
Would you tank your career, and only have the apparent lost salary compensated, and only during marriage? Could you even keep your high earning job at 40%? You want nothing for the fact that you’ll probably never get a promotion again?
As I said reducing work equally is easy but not sensible. Compensating lost opportunities fairly (and both perceive it as fair) is really hard.
I think the main issue is to get wife agree to live life post-marriage based on her own capabilities (education/work experience) only if she did not do any adjustments to cater family more than you. If she does, then she needs to get compensated.
Btw, 50/50 split is only on 1/2 pillar and assets that has been accrued during marriage, right? Seems fair to me.
Exactly, it wouldn’t.
You could also look at it from another way. Let’s say you have 2 kids but you both keep working and you hire a nanny. Because both are still working you would split the costs for the nanny just like the other costs (which I think is already pretty generous of you to pay according to the difference in income).
In that case both would contribute to the increase in networth equally in % of income. I don’t think that she should get more of ‘your’ money if you divorce. In case of a divorce just paying for the children can already be really expensive and leave you at the existential minimum.
I personally would never get married as I don’t think that the government/somebody else should be involved like that in your relationship. From your point as the main earner in the relation there are just too many downsides. What really is the upside of marriage? Showing your ‘true love’ based on an old concept?
Maybe we should give her the benefit of doubt. Where do 100 nailstudios get their produce and why should she not be able to get into B2C by buying and selling wholesale? Maybe she will want to generate income, even with future children?
And if the judge concludes that your future income/revenue stream was insufficient for the security of the alimony; he will still just distribute your wealth no matter what. Same if the judge considers the wealth split was not fair.
There are many people that in hindsight recognize the notary money for the wedding agreement was a waste of money.
So better not marry at all?
You seem extremely concerned about this, very emotional. Not meant personal but potentially she is not the right one for you or the timing is simply wrong?!
I would consider not marrying now and reassess the situation should you have kids. This will change everything anyway…
No. marry, but only if you are fine with the financial risks. Personally - I would any timenmarry my Partner, but she doesnt like the increased taxation 
If you worry financially - then yes I am not sure if you should marry.
IMO what doesn‘t work anyways are such discussions in absolute CHF terms since they will change anyhow.
Heres how we did it:
not married due to income tax penalty
we both pay 50% of the household expenses (incl. 1 kid)
Now the rule I came up with is this:
IF one partner works less to take care of the kid, the working partner shares 50% of the income generated on that day (after taxes).
Doing so, she basically makes it possible for you to go earn big money while she is taking care of the kid, so splitting it like that is fair - but only then. If the kid goes to KITA and both are working I dont see a fairpoint in a split at all…
Works very well in our case (with a kid) - was put in a konkubinatsvetrag with a lawyer & notary.
Having such an agreement is key in my opinion, married or not. Worst case is bot talking about it at all.