A) Here is the Blouse with a detached key-hole type neckline. To simplify things even further, just finish it with a binding. Pull the look together by binding the bottom edge (instead of hemming) as well.
B) Adding a collar is slightly more complicated, but the easiest one to make is a band collar.
You can just cut a straight strip of fabric (A). The band will gape away from your neck, as shown in the pictures above. For a closer fit, cut strips that curve slightly (B), and the band will hug your neck more snugly.
C) The pattern also can be adapted into a dress by just extending the length of the pattern from the waist.
In an upcoming post, I describe in detail how to add a flat collar to this pattern, but the method will work for any blouse pattern with a flat neckline.
The Versatile Blouse is available here.