That’s the way I would try to set it up too. If you don’t want to have to unlock your system everytime just to boot into Windows, you will need an unencrypted /boot partition. Either EOS’s or that of a 3rd system.
I must confess, the only multiboot system I have is a LVMonLUKS Arch install with an unencrypted boot partition and Windows. So no problem there.
All my other computers now run a single Linux system with an encrypted /boot. I really dig the btrfs snapshot rollback feature and don’t want to miss it anymore (I also use lvm-snapshots on my ext4 setup, but the restoring/rollback process takes more time and in my case always requires it being done from a live environment; it also has the described potential kernel rollback problem).
I guess my next project will be thinking about how to multiboot “efficiently” without sacrificing an encrypted /boot and the btrfs snapshot feature.
Please report back, if you happen to set this up properly.