Hmm, do you really need an attic of that height? If not, just cut off the curtain wall so that it matches the top of your angle profile (variant A). That's exactly where the water proofing may end (in Germany, you have to go 15 cm above the general water proofing level).

Is the front sandwich panel an asset in the building's elevation? If not, omit the panel by raising the glazing to the top of the lowered attic.