I bought a pair of Roland System-500 sets to give my Oberheim DSX something to do with its CV/Gate outputs. Four Juno-like voices either as a poly stack or four separate parts. The remaining 4hp in each case are used by 2hp Buffs to split the pitch CV between oscillator and filter, 2hp Mix to get the four voices down to one output, and 2hp Trim to patch between the LFO and the Hosa Knucklebones for consistent vibrato and PWM.
You can hear it play a Juno pad here:
For the next phase, I plan on adding a sub-oscillator, extra envelope, and noise source: 
What should I do with the 40+ hp left? I'm torn between adding a wavefolder per voice, alternative (multimode) filter per voice, or Black Sequencer for future live use.