You have recommended a French-cut shirt without learning anything about the character he portrays. Bit premature of you.
In period... shirt styles were transitioning from square-cut to french-cut. Young dandies and men who were buying their shirts ready-made were likely to have french-cut shirts... would have bought them in boxes of three to six at a time. Older and younger established men who were getting shirts made for them from female relatives or custom-made from a professional shirt-maker would be very likely to still be wearing the same square-cut shirt pattern that they've always worn, updated for "size" and collar style of course. If his character received the shirt while in the field from a care box, it has a chance of being either style.
From a modern standpoint, the french-cut style will "feel" similar to the fit of a modern dress shirt. The square-cut shirt is dead easy to cut out and to put together... because it's name says what it is... squares, rectangles, and triangles. The stitches you'd be using to sew one by hand would include a "run-n-fell" a "whip stitch" and a "buttonhole stitch."
Bringing the