Increasing if you ask me, I agree with you.
OST has basically all the big exceptions, with the leFH being the biggest one.
The Walking Stuka does minor FF, as does the Panzerwerfer. Seriously, Pwerfer your MG next time someone rushes it and it'll walk away.
Off-maps have full Friendly Fire to my understanding
Interestingly, the UKF Base Howis count as off map, not on map and as such have full FF. I've wiped a few of my own squads with those 25 lber rounds. That's how I ended up digging up the stats you now have.
FF should be standardized. Either let us charge through the fire, or make FF a real threat. The issue is, on-map artillery is already standardized against FF and off-map artillery is standardized with FF. Mostly. That would make the game more consistent.
I'd advocate FULL DAMAGE. Bombs don't have an allegiance. Don't forget that Grenades ALSO deal minor to negligible FF.