Thanks for the tip, I will put this suggestion.
Look, in fact this is very common, very much, more than everyone thinks. I have been working with Construct for many years, and many clients just want to change images after the game is ready.
And as it was before, it was very simple for anyone to change the images of the game. Just open it in Photoshop (example), change the image and save. Now, it is more complicated, because there is no way to know the limits of the original image.
It is a pity, I think this optimization should be optional. I know all the good points, and I totally agree. But I think it should be optional, in small games it wouldn't make a difference.
I will send this suggestion. Thank you all.