When I was at Amazon (ie until last Friday). We had three options - sell all, sell enough to cover taxes, or sell none of it and pay taxes - some other kind of way that I never looked into.
Even if that’s not the case, what’s stopping you from selling enough stock yourself once they vest and make quarterly payments?
My tax rate was 22%+7.3% FICA near the end when I moved to Florida - a state with no state income tax.