Capacitors as sensor output data storage?
Given a suitably modest accuracy requirement,  large capacitor, high-impedance op-amp and low leakage conditions, it is nominally possible to do as you suggest. But it is unwise for anything more than a short period.
The main problem is that charge leakage will be unpredictable and may vary a great deal, with environmental conditions affecting the conductivity of the air and even condensation on the hardware. Dirt will accumulate after prolonged use and further degrade accuracy. Military-style encapsulation would help, but requires skill and experience to do well.
Charge-coupled devices (CCD), once widely used as camera sensors, are capacitance-based and implement a more complicated variant of just the principle you describe, but the charge need be stable only long enough for the CCD array to be read out into digital storage via an ADC, a time measured in seconds at most.
In practice you would do better to go down a similar route. And if you are doing that, why bother with the capacitors?