Layouts without predefined column-widths


the new layout field is fantastic. Many website projects I work on are portfolios for artists or design people. And I wondered if there is a way to give the panel user free choice over the 12 columns?
In the reference it just states that >>The layout field supports up to 12 columns and all are listed below.<< And especially with these kinds of clients, who are creative and have some background in indesign&co, I feel like for some projects there is no need for me to predefine layouts, but rather give them full choice. So they can go 5-4-3 or 11-1 or 5-5-2 or whatever.

In the reference, it looks like its meant to be rather static. Could I query the layouts from a different input, so they could at least define-layouts on their own in a different tab? Or event better could a plugin intercept the call of the layout selection popup and just puts in some number fields to enter “layout numbers” instead?

Thanks for any hints,