To the point of maybe shipping the stock FP Camera app with custom ROMs, what is the state of FP Camera in LineageOS? Does it work without issues when installed with the necessary permissions and in /system/priv-app, or are there still problems like you mentioned?
I can get wide-angle working in Calyx when the app is started from a shortcut (has been mentioned somewhere before), Pro mode works fine as well, but the main activity keeps crashing on me. Videos don’t work either and 48MP just produces even lower resolution pictures than the regular mode 
Are those known problems or am I missing something obvious here? 
CalyxOS is pulling in some proprietary blobs by default, but compared to a stock /vendor/lib64/camera/ directory, there are several missing.
Is that it, do I just need all the things? 
(Sorry if this is a stupid question, I have absolutely zero experience with low-level Android stuff)
Edit: I’ve moved my question to this topic, seems like the more appropriate place.