Ask HN: Migrate a large corporate system with strong relations to Firestore?

So i have been assigned with the task of migrating a large corporate system running in production to Firestore and cloud functions. At the moment the system is a JS framework with thousands and thousands of LOC, and the task of porting that to cloud function without having any data relations seems daunting to me to be honest. Not that it can't be done, but i feel many of the solutions to replace RDBMS seems so hardcoded and hacked to me at this point. Management have proposed it as a fresh start to rewrite the entire current system, after reading a bit about Firestore, and want to get offline data and get the strong authentication scheme from Firebase, but these features could fairly easily be implemented otherwise. So i am hoping someone here has had some experience with migrating large frameworks with strong data relations to Firestore/NoSQL frameworks, and replacing an entire serverside with just cloud functions?