That’s not a new business idea. It’s been a thing since they announced the new guidelines. You can just buy the stuff https://www.amazon.com/Stage-Mix-ins-Allergen-Introduction-A...

My wife and I were always going to feed our child anything and she’s liked eating food off our plate anyway since she was 6 months old or so, but it was something we considered. So far the only thing we haven’t given her is shellfish.