You're looking at this wrong. No one starts negotiations where they want to end up. They're starting at secession, where they want to end up is federalism.
Imagine how much more prosperous and progressive your blue panacea could be if the backwards red states had no say in your laws anymore!
You could perform gender reassignment at birth, create taxpayer funded abortion-mobiles to travel from one office building to the next so women aren't burdened with missing work for it! Down with the patriarchy!
Heck, you could make all the rent and colleges free and shutdown the evil private schools! Oh, and abolish grades, they're racist! Probably need to force all the white male professors into retirement too, you guys certainly don't need to hear from THEM again this century.
Ooh ooh ooh I know! Put all business under control of the government, make union membership mandatory, and take away union rights to negotiate because the government knows best! (They can still funnel dues to Democrats though.)
Dude! I've got it! You're gonna like this, it checks a ton of boxes. One bill, okay, you wrap all of these objectives into one historic bill:
1.) Universal Basic Income. This is the foundation. It has to be enough for someone with a family to live comfortably on. Enough to cover basic human rights, like food, iPhones, PlayStation 4, 70" 4k surround sound smart tv, new car, ocean view home.
2.) Universal healthcare. Of course it will be cheaper without the red states, and with everyone having lots of time to exercise since they won't need a job thanks to UBI.
3.) The coup de grâce, the cherry on your sundae.... open borders! There's going to be plenty of people who want to enjoy the new utopia (nation name idea: Newtopia!) and you guys aren't cold hearted so you would never turn anyone away. The added perspectives of millions of new citizens will help you come up with even more ways to help the citize...oops, that word is racist, even more ways to help the population prosper.
This is quite an opportunity for the blue states.