I propose that Chroma's 1 switch off when you swap elements. If nothing else is being changed about it.
If more changes are on the table, I propose that his 1 become an exalted weapon, with the projectile type changing with the chosen base element, and the base damage type refusing to participate in combination elements. Like if you want rad damage on your fire breath, you should have to put both a +heat and a +electricity on the weapon and only the heat from the mod gets in on the radiation.
Heat damage should be delivered in a long and glorious beam of furniture-melting plasma.