Start a company using FaaS as your base backend technology, run it for 18 months plus, through at least one funding round (and due diligence) and building a team around it (to learn CI patterns and code sharing)
Something like that
Another option is to be in a big org and take on a project and make a FaaS your base backend tech and see what happens over 12-18 months through multiple iterations and team growth.
There are things you don't fully understand until you have to share code amongst a wider team and also until you have to justify some of the technical decisions you're making.
Some of the things you think should be clever are missteps