Here is an intriguing tip from Ruth Wyeth Spears for her 1920s home sewists. Detachable shoulder straps of ribbon and elastic is a gift you might not think of! Designed for use with undergarments (such as a camisole or slip), the shoulder straps are attached with tiny safety pins. Ruth suggests tiny rosettes of ribbon if you want to make them fancier.
This idea is very simple, and certainly useful for 1920s undergarments. Rather than making the shoulder straps detachable, I think it would be great to use them in place of regular straps in slips, camisoles, and such.