I am contemplating using a basic VCO to design my own kicks.

You can do that easily with any basic vco. Plug a decay into V/Oct and another decay for the vca. Trigger them together. Works pretty well! Using two separate decays gives you more flexibility to scale both level and length of the V/Oct decay.

That being said, I can recommend the Can I Kick It module from Skull&Circuits very highly. It has two of these circuits. You can control the V/Oct and VCA decays separately, but also cross-modulate them for more fun. It's a very good sounding modules with a bone piercing kick. There's also a pitch in. While it's not V/Oct, with some scaling I managed to use it as a bass synth

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