A voltage controlled varactor can be made from 2 non-complimentary mosfets with a common body bias. The differential amplifier can be done with as little as 3 additional fets, but probably more on the order or 7-10 for performance reasons. So you're looking at programmable on chip integrators for around 10 mosfets a piece. Of course, you'd use a technology size larger than what is used for digital logic because the analog toolchain would be more sensitive to problems like channel noise, gate tunneling, etc. You would not want to use a differentiator because they tend to amplify noise in an unstable and uncontrollable fashion and are not required for functional completeness (the analog equivalent of Turing completeness).

Edit: IQ analog processing is extremely common in the high performance RF field but tends to be static and not reprogrammable. FPAA's exist on market but are extremely expensive for what you get. The general purpose analog computer was initially developed by Shannon (yes that Shannon) back in the 40s.