It’s funny, whenever I bang my head against a problem long enough to reach out for help, I end up solving it shortly after. Something about typing out the problem makes it easier to solve, I guess.
Anyway, the solution for my case was to punt and simply create a child component of the OpenGL component which uses “normal” JUCE Graphics painting. The OpenGL component can then call triggerAsyncUpdate() to trigger a child paint, which then calls a function back into the parent. So all the code still lives in the parent, making the actual lines of code changes extremely small. Side benefit: No more expensive Graphics object construction needed at every call of renderOpenGL.