Here's the thing. A user at http://highscore.com posted a play video of a game for the Sinclair ZX Spectrum. Actually, this shoot 'em up has all the makings of a great homebrew conversion for the Atari 2600. The Game is called The Pyramid. It was designed by Bob Hamilton, Darren Hamilton, Ian Hamilton, and published for the Speccy in 1983 by Fantasy Software.
Here's the video. Take a look and please comment on this idea: