I’m not sure if it’s precisely what you’re looking for, but… I do all my signal routing through MixerChannel (I forget if the quark is named ddwMixer or ddwMixerChannel, I think the former).
It automatically manages groups, buses and execution order between mixers, keeps source and effect synths separate, and offers post-fader and pre-fader sends. The design is basically unchanged since 2005 (which means it’s stable, mature, and has handled everything I’ve thrown at it for over 15 years).
If I understand your use case, I’d have an effect synth on the percussion channel with a control input for what you’re calling “volume.” If I then map that to a GenericGlobalControl (ddwCommon quark), then I can stick a GUI for the GGC object into pretty much any GUI context.
I’m not totally clear what your “dynamic EQ” is doing, so I could be off base. Just mentioning that there’s at least one framework to make group/bus management about as close to painless as I can imagine.