Going DW Rahzin you get over 100% Pierce > Chaos anyway however its a bit underwhelming to see RoS (probably the biggest AOE the build has) not to change visually to reflect that its 100% Chaos damage.
We know that partial conversion doesnt allow for the visual dmg type change and for that you need to have a hardcoded mod 100% > to something.
Proposal is just to add a mod somewhere on Rahzin (maybe amulet) - 100% RoS Rierce to Chaos in order to allow for the color swap.
Its not a buff more like a workaround to enable more chaos visual pleasure.