This is my take on a Chroma Rework you are free to have your own opinion so here's mine.
Passive: I don't mind it as is maybe add an additional effect if you really care that much.
Spectral Scream: Same as before with some buffs to range and damage with the addition of holding down the trigger to focus into more of a beam that increases range and damage but also drains energy faster.
Dragon's Hide: A fusion of Elemental Ward and Vex Armor I don't have any specifics in mind at this time.
Ruin: Chroma's Effigy flaps it's wings and sends out an elemental shockwave the element is of course dependent on emissive color while used with Effigy active the blast will fire from you and your effigy at 50% range and strength.
Effigy: Same as before but with less energy drain with option of keeping the pelt on and to fly/float around kinda like HIldryn's 4th but while active in this way energy drain increases while other abilities gain additional strength and range.
This is all an idea you don't have to agree with or like it but with all the new mechanics brought by the warframes that came after Chroma's initial release I believe they can make this happen and give the Chroma fans that like his abilities and the ones that just want to fly around as a dragon what they want while also making him more versatile in missions.