The original game came with a 'map' of the tech tree, which I'm sure was a great help to players who had it; GOG's version is rather noticeably lacking any copy of this map. Is there some way to propose to the GOG admins that it be tracked down and added?

If so, I could note that I've found a high-resolution scan of that map of the tech tree that came with Alien Crossfire after a bit of searching the web; it can be found (apparently I can't post links?). (A direct link to the full-size image can be found (apparently I can't post links?).)

While the scan is not perfect, it's the best one I was able to find in a brief search of the web; it may be possible that Firaxis still has the original design files, which would be undoubtably the best way to go if GOG can negotiate access to them to produce a high-quality PDF or image.

You can! If you go into support, click "contact us." Chose the other option which gives you a form with the option to flag it as being about bonus material.

I included a tech-tree related application in my thread.