As a suggestion, I think it would be great if we could add what kind of demo each one is, because some are just portions taken directly from the full game, but others offer original content not included anywhere, which is a difference that could be interesting.
The Information you do read here comes most likely directly from the GoG Database.
If a new entry is found, it is posted in here.
For everything else somebody would have to play the full demo and for your idea, he would have to play the game the demo is for.
If you want that job, its yours.