If people used a 2D engine which already had everything premade for them, it would actually be quite easy.
An engine is generally a compiled library, unless it is open source, and even then, it is a lot easier to use that library than rip the source in to your own program. I think people should just do what they want. The more varied the submissions are, the more interesting it gets.
That would be cool as well. Make it a variety so the judges don't make their mind up on the first really good one.