I'm pretty sure the reason Minko didn't want to add the Omurice was due to the fact that it was simple and she couldn't show it off to Tohru. Not that it was hard to make, or hard to make it taste good on a hot plate.
Also, omelet rice is easy as all hell to make, even on a hot plate (electric too). I've done it before numerous times. It's also facetious that she's trying to cook Jibuni with Beef (not to mention Beef takes much longer to cook than eggs) and Miso Mackerel which is a much harder dish to make than a simple Omelet Rice.
edit: Although I could be wrong in the fact that Minko or the show's creators do in fact believe you can't make an Omelet Rice that tastes good on an electric hot plate.