I reckon you'd be silly to build anything off that tbh.
Made the same mistake about errr...18 months ago. I forget...could be two years.
If it's a one off theme just use regular sections and accentuate metafields for the flexibility you need.
I ment for my self. I got a store today, built on a 3rd party theme, but as those usually contains 2000 settings I don't need or use, it's a mess to update and feel a little slow. But I do like how it looks and perform. My plan was to rebuild what I got, but into a new clean code base I control and then duplicate that into 4 other stores I have.
Just don't want to spend a week building ontop of Debut (as an example) and end up in 8 weeks having to redo the whole thing.