So far, I have two TNT patterns for tops for M that I can just cut out and sew without any fitting. I use features of both patterns to fit new patterns. The first success was New Look 6027. Many of the New Look patterns have a shaped back seam that keeps these tops from looking too loose. I often transfer the back curve of 6027 to other patterns. I have made lots of these and am still playing around with the pattern.
My second success was NL 6871. The back of this one lacks a seam, so I added one using the previous pattern as a guide for shaping.
This pattern should be easy to alter, but I need to find some lightweight cottons with good drape. Or some knits.