Nice idea. Unit handling can be hard though, there are several problems that you can bump into:

- It's not always evident what unit you want show after a calculation. (As/Vm or C/Vm, kV/m or V/mm)

- You should handle fractional power of units (like V/sqrt(Hz))

I recently discovered orpie and that one has unit handling. It has electrical (and all sort of physical) units and handles both of this problems fairly well. For the calculation result's unit it uses the one that comes evidently from the source terms (1kV* 0.5mA=0.5kV* mA), then the user can convert it to other equivalent units or to SI base units. It's an RPN calculator so one has to get the hang of it.

Edit:

Oh, electric engineers like to think of "rad" as a unit (like in rad/s and Hz). I think it's impossible to handle it well.