That strikes me as a terrible idea. His plan would have the founders constantly second-guessing each other over reaching milestones, and would take ordinary disputes ("You never start work before 11AM"; "The design work is taking 3x as long as the development, you're a bottleneck") and turn them into knock-down drag-out brawls over equity every few months.

I'm a fan of splitting things up at the beginning, attaching a vesting schedule, and having everyone work as hard as possible.

You also shouldn't have this conversation until everyone's committed to working full-time on a business. Trying to give equity to someone who has a day job and promises to leave "when the new business is really underway" is a disaster in the making.