I've been searching the interwebs trying to find an edible gold to use on IMBC.
I like the ease of use and the pigmentation of the Edible Art Paints.
However, it is not recommended for IMBC. Why? It tastes awful, very bitter, and doesn't quite dry.
I know this because I tried.
Everything I've read so far suggests that painting on a crusting buttercream gives the best results.
So here's my conundrum. I always use IMBC. 
I do have an airbrush and I have airbrushed metallic gold on IMBC without issue.
It's the more detailed stuff, like painting names or painting the crack on a faultline cake.

I'm not sure if there's such a thing as a light, fluffy, not-so-sweet ABC with the same texture as IMBC or if there's a better (FDA approved) edible "paint" I could use?

not exactly — unfortunately textures are not interchangeable between different recipes and abc is made from sugar — what about a 50/50 mix but use white balsamic vinegar to cut the sweetness in the abc part — maybe 

it’ll be a new texture of course and flavor too 

Roxie and Rich make an edible gold dust which can be combine with alcohol to make paint.  For IMBC, you could use cocoa butter as the medium for mixing the gold dust, sort of like oil paint, which would be more compatible with the fat in IMBC.

 hey — looks like last call — the lights are flickering here —

let’s meet up on  “keep calm and cake on” on fb