Those failures actually look more like a bug in the gauges, rather than a modeled failure, as it's not very consistent. Oil pressure and attitude indicator should work without electricity, and since other electrical instruments are still working, this seems more like a random glitch.
Here's a circuit diagram for a Super Cub — and it doesn't look like it could explain your situation:
Ha this could be it. The oil pressure gauge has some kind of built in failure table and the action is kill the electrical system. Don't ask me why it would do that now.
This is interesting. From experience I know that the options to model the effect of exceeding aircraft limitations by .xml gauges are limited. I could imagine that generating an electric failure may have been meant as a warning finger. The alternative may have been to generate an engine failure. That may have been thought of as pretty harsh ... and not really realistic either.
We probably should mention this as a comment in the aircraft table