Just after I wrote that I have to give up on the feature, I managed to defeat it :D

My idea with the new property for the original viewport via patch worked (I'll be honest here, I wouldn't be able to make it without AI which a friend recommended to me as good for coding one). After a few hours of battle with bugs the first version of patch caused it worked as intended.

Marvelous.

Now I'll go get some sleep ((x