>we need the ability to persist a design

isn't that Textual Inversion (https://textual-inversion.github.io/ ) ?

It's more or less implemented in some forks (e.g. https://github.com/lstein/stable-diffusion#personalizing-tex... or https://github.com/hlky/sd-enable-textual-inversion (discussed previously ( https://news.ycombinator.com/item?id=32643564 ) )