This is obviously a (hacky) work-around. Firebase Functions are designed to be deployed individually- abandoning that costs you GCP log traces and boilerplate right off the bat. Read the Firebase Functions documentation, and you'll see no mention of designing your application this way.
Sure, maybe I'm reacting more to calling it a nightmare. This is a well documented limit.
First thing I always do is read the quotas/limits on any google cloud product before I use it.
Then, I'd notice the increase in deployment times on my CI server as more functions were being added and inspect what was taking so long and try to optimize it. Those individual endpoints take a while to deploy...