Actually I think LGPL is not trivially compatible with audio plug-ins. Or have not heard proper workarounds for the following problem.
The reason is that plug-ins (VST, ...) are always distributed in such way that the source is not available. LGPL wants the source of the LGPL'd code distributed, which is impossible other than by, for example, providing the LPGL'd code (e.g. as a .dll) in the .zip file the plug-in is distributed in.
I don't know how Cabbage's license relates to the license of the produced VST. The VST SDK is known to be incompatible with GPL code, since the VST SDK cannot be distributed (it's proprietary), thus VSTs cannot adhere to the GPL. I don't know how you've worked out that Cabbage can be GPL, but produce VSTs.
This should be clarified since to me Cabbage seems very suited for developing certain kinds of plug-ins in the style of "SynthMaker" that benefit from a large library of pre-made stuff and a simple and fast to use "scripting language".
You should also clarify, how is Juce used in Cabbage. Since Juce is commercial software if producing commercial VSTs.
If it turns out that Juce is creating a problem, then I might recommend porting Cabbage to WDL-OL . Or I might attempt it myself.