I have a few thoughts:
The filters and VCO's should sound great together, and the noise/s&h is a great addition!
You could really use a VCA and mixer. Some modules contain both. I recommend checking out something like Befaco's A*B+C, which can act as two 2 channel mixers, one of which has a through-zero VCA, allowing for both +V envelope cutoff's and ring modulation, which would be extremely helpful for weird drum sounds; or Mutable instruments Streams, which has its own built-in envelopes and a vactrol emulation mode for a LPG effect (in case you want Buchla bongo-type stuff, although you'll want an additional mixer).
You'll also want another oscillator or modulation source. I'd even consider replacing Pittsburgh Modular's ADSR with something like Mutable Instrument's Peaks, which can handle multiple outputs at once.
I'd also recommend not ruling out starting with an all-in-one semimodular. Pittsburgh Modular's Lifeforms SV-1 sounds phenomenal and has everything you want. Or even build around what functionality it appears to offer. There's plenty of options out there, but you hit on the majority of what you'd need for a decent monosynth or drum+snare system.