I made the sleeve narrower and took some 12 cm off of the sleeve pattern. There was still plenty of fabric to gather around the cuffs.
I made the whole blouse using French seams.
I removed the center-front seam. This is how the wrong side of the garment looks like. I turned about 6 mm of the facing edges under and topstitched them to make the facing look nicer. You can also see that I replaced the clasp with some ties.