I work 99% of my knitting in the round, and like a good Elizabeth Zimmerman fan I often make a swatch cap, or a mitt, instead of a standard swatch-in-the-round. Plus-side being, you get to wear your swatch afterwards; although beware of over-indulging in your swatch-accessory, and then having to play yarn chicken. Never a good feeling.
The other swatch/project I’ve been known to make is a doll-sweater. Of course, the difference in scale between this and your planned human-sized garment means that the doll wears a “chunky knit” version, but it can give a good idea of colour combinations, especially with a little head popping out of the top. And the doll-clothes reserve has one more item added!