the answer to your question depends on exactly how you are to design your model and what you intend it’s use to be but there are two options that could be viable approaches:
1. Determine a current that does not change in your cell/ disease of interest. the simpler the configuration ie fewer configurations, subunits, modulators etc the more reliable you’re model will be. Quantify the current and perform single cell RNA-seq on the same cells as a dataset from which to extrapolate your model e.g. https://www.mci-neuroscience.com/integration-electrophysiological-recordings-single-cell-rna-sequencing/
2. again cell/ model/ disease dependent membrane capacitance can be used as a proxy measure for cell size and cell size is also roughly proportional to genomic material within a cell (with many caveats) Article Nuclear DNA Content Varies with Cell Size across Human Cell Types
Thus membrane capacitance recordings may equate to D/RNA content depending on the utility of your model.