Couple of notes I'd like to throw out there...
- The Serverless Framework does help ease quite a few of your concerns, local development is made much easier (they have a node server for js development). The company working on it is kinda funny, but I still think it's a good tool. I currently use the raw lambda environment at work and can say that the serverless framework is a valuable abstraction.
- I think Cosmotic is making their deployment setup more complicated than it needs to be. I obviously don't know their use case but there are easier ways to accomplish a CICD w/ FaaS...
- I would recommend trying it. Its pretty painless, and you'll know within ~2-4 hours whether or not it will work for you