I would just stick to eurorack levels(I’m a modular guy too), as that would mostly be the form factor people would be dealing with when using gates&cv I assume. Also, as your big-genes module is already eurorack, it would only be logical to make it fit the same form factor.
Another possibility would be to use midi, but in that case you’re limited to 127 steps, which would cause aliasing and timing problems when generating multiple fast continuous CV signals like envelopes and lfo’s (although using some already existing cv2midi module for extra controls could very well work).
Last thing… are the CV inputs over-voltage protected on the board itself or is that taken care off in the big genes module? As some (imo badly designed) eurorack modules can produce some really high voltages or spikes…