@ElMiko - the reason why it isn't integrated into the metadata download plugins is discussed in
this thread. Basically it just isn't technically possible with the way Calibre works currently, and the intersection of those who want it vs those who have the knowledge of how to change Calibre to support it hasn't met yet
So that means it can't be done in a metadata download plugin. Could it be added to this plugin? Technically it would be possible. The main reason why I haven't is holding off to see if it was possible to do it with the metadata download plugin instead, which would be a better place for it imho.
If I did add it to this plugin, it needs some thought as to how it would work. For instance, does it become another "Page count algorithm" choice in the dropdown, so that you could choose Goodreads (or Amazon)? What does the plugin do if it cannot find the book or the book has no page count specified (not every edition on the website has page counts)? Does it leave it as zero? Or does the plugin have to support some sort of fallback option? People mixing page counts generated by the plugin vs page counts from the website could end up with a bit of a mess, but maybe that is the exception.