I think GOG should implement an archive sync function. So that the client can check if your downloads (or entirely library as in my case) needs updating. Because of new patches, updates.. or even a user requested archive validation.

This way it would be much easier to make sure that your downloaded archive is in good shape. Especially since bit degradation is a real thing, and all data stored on hard drives, Cd's etc.. get corrupted eventually. And without trying to load the actual data, there is no way of knowing a corruption have occurred.

Please note, that this isn't the same thing as checking installed games. I'm talking about the downloaded archives.
Not even Steam checks that.. until it is actually installed. So what I'm suggesting that it should be possible to actively check if the archive is OK, without installing it.

I think what you're looking for is gogrepo

gogrepo takes some setting up, but I wholeheartedly endorse it.