I created a corresponding wishlist entry.

As far as I understand GOG's recent marketing decision, they would like to promote the use of GOG Galaxy and help new users to have the most comfortable experience concerning updates, cloud saves etc..
This led to quite the uproar, as this tactic is being perceived as an intrusive bloatware practice.

I think it is easier to promote the use of GOG Galaxy for new users if it would just be automatically added to everyone's accounts instead of bundling it with the offline installers.
Therefore, new users would immediately be aware of GOG Galaxy's existence and features and could make their own decision about the use of the client.
In addition, you could simply add a page within the installers and link to the account page.

What do you guys think?

Completely unnecessary. A link to the Galaxy page exists above every single installer. No need to add yet another one.
https://www.gog.com/upload/forum/2017/05/a154ff81bd25b51699cfedd4c5088fc1eabfb37f.jpg

As I said, this new measure is not aimed at the people who visit this website or already have an account on GOG. So your solution wouldn't provide what GOG is aiming at.

Come on,who would be silly enough to use a torrent site for a free Galaxy?

Which means they are trying to use Galaxy as surrogate DRM.

No need to polute the Library with it. Actually I wish there would be an easy way of removing demos for example. I hiding them but they are still there.

I thought of something more prominent, like an extra item on the account page, so that new customers would quickly stumble upon it. I honestly didn't notice this button until you pointed it out. If you assume that the bundling is directed towards pirates, you are right. I don't think that this bundling has any effect on pirates whatsoever.