Cultist Bows and weapon modifiers

So i am seeing this bow over and over which has chaos as base damage and keep thinking wtf to do with that. Its kinda similar for the lightning staff. The idea to have different base damage is nice since you can create so many more bases but does it work with the current mods?

For the lightning staff you could say get a flat light roll and ele dmg with attacks but what about the chaos bow?

My proposal: Ditch the increased phys dmg and ele dmg with attack rolls and make a local increased weapon damage modifier. Equalize the flat mods.
Then you could have base types like the cultist bow actually scale its chaos dmg via this mod because currently there is no way, there isn't even flat chaos damage. So what you gonna do, hope for a double phys roll and some conversion? Like thats likely with the limited crafting we have.
So basically my question is: why is phys damage and any other "element" treated diffrently? If you would treat them equally there would be no need for all this conversion crap, you could just roll flat cold damage and increased weapon damage as per my proposal and similar for all damage types.

Cheers