C++/Juce Sidechain FM audio plugin

In the analog audio world, frequency modulation with a sine wave is simple enough, and introduces no latency. Surprisingly, more complex waveforms can also be processed in this way, both as the carrier and the modulator. However, in the digital world, complex frequency modulation algorithms are exclusive to expensive VST plugins like Serum or Phase Plant. Even so, these programs use predefined oscillators with clear pitches to define the FM, and it isn't even true FM. That's what I know so far.
I'd like to ask the more experienced members of the VST building community if something like this is possible and if this has been attempted before: Smoothly modulating a signal with a sidechain signal through a DAW.