Take over percentages from the father

Hello, I have a somewhat special question. I have insured my car as a second car over my father’s liability. My brother has also insured a car as a first car over my father’s liability (45%) + all-inclusive (45%). Now I want to buy a relatively new car next year with which I then also need a comprehensive insurance. Since I am currently only driving around with liability I would get into it with the all-inclusive relatively high next year. Now I wanted to know if me n plan would work that way. I want to get my brother to re-register the insurance on his name and take the percentages he currently has about my father. My brother drove the percentages down so it would have to work. Then I want to register the new car that I buy a few months later on my father as a first car so that I get in with lower percentages. Would my plan work? The decisive things are whether my brother can simply take over the percentages and whether the percentages are still available with my father as a first car so that I can use them. Wouldn’t be bad if something like this works because comprehensive with high percentages is expensive. Is a bit complicated but hope you understand what I mean. I should actually know this the insurance questions but wanted to inform me in advance already if this is realistic, because it still has time until shortly before November.