@K.C. Lee suggested using a resistor divider network with a bias voltage to scale and shift the +/- 10V to 0-3.3V. Duh! Why didn't I think of that? Added a LTSpice schematic and output plots of a circuit that gets the job done. I've already ordered the uber expensive LT op-amp, switched capacitance bipolar power supply, and linear regulator for the gen 1 design. Diligently pursuing sunk cost fallacy, I will build up and use the op-amp version for now. For the cost of a semi-precision 10V linear regulator and a few resistors I could've been down the road. Live and learn I guess. Thanks again @K.C. Lee!