Are there any updates? The current situation with the VST3 layouts is not really suitable for inputs/outputs being independent of standard loudspeaker layouts. See this thread: VST3 Bus Layout Issue - VST 3 SDK - Steinberg Forums
Especially for Higher Order Ambisonic plug-ins, Wave-field synthesis, multi-source encoders/renderers, loudspeaker decoders for arbitrary number of loudspeakers (e.g. for HOA, VBAP, …).
I am not really familiar with what’s going on within the VST3 standard, but I guess a quick solution would be allowing discrete channels as a default layout, so DAW / plug-in host manufacturers can allow non-standardized loudspeaker layouts.