In my opinion, it would be way to much a waste of time to script up the engine so that it makes levels for you. Not to mention it might do stupid things like texture a block you don't see. I say make one good level instead of trying to make tons of random levels. The random caves and stuff were cool at the start when you really didn't know anything anyways. Later when you had to make your way to the bosses over and over and over, it got stupid.