Starting Seeds in Pots

Would it be beneficial to start seedlings by planting seeds straight from the seed packet approximately one quarter inch (half centimeter) deep into a pot, water until saturated, set outside, then cover the pot with a thin plastic sheet ( like freezer wrap)- to keep moisture in- until the first seedlings sprout and break the surface of the dirt?

The method you describe would work for a lot of seeds as long as you made sure to keep the pot in shady spot so that the sun can't cook the contents of the pot.
However there are plants such as foxglove that must have light fall onto the seeds for them to germinate and others such as echinacea that germinate better with light and these would have to be merely pressed into the soil surface and the place chosen for the pot should be a bright spot out of direct sun.
Also very fine seeds might have difficulty emerging if planted half a centimeter deep. A general rule of thumb is to cover seeds with twice their diameter of soil.
The plastic wrap is a good method of keeping the soil moist, but watch very carefully that some fungus or bacterium does not start to grow too and kill any seedlings. If you see any fuzzy white growth or a slimy layer forming on the soil surface, give more ventilation immediately.