One important factor that stands out to me is that if modders can make different weapon frames that can accommodate different size barrels, stocks, sights then the variability in weapons will be gigantic. A perfect example of this is the PC/PS4 black light retribution which has a satiafyiny deep variation for weapon models.
I'm just hoping anyone considering making new weapon mods is aware of the potential here. It's the first time in a Beth game that really unpredictable loot can be achieved. Would add heaps of gameplay longevity to me.