I wasn't sure what you mean by keeping the same ration and pixel scaling, as when I go fullscreen with Alt+Enter like in most RPG Maker games (or F1 -> choosing to start in fullscreen), the game retains its aspect ration for me, and in multiple computers. However, after doing a brief research on the subject it seems that the scaling of the game is handled by your graphics driver rather than the game itself, so it appears to be a limitation of the engine and one I had no idea even existed!
And unfortunately I don't have RPG Maker at the moment so I can't make modifications to the game (unless if it's for something like a game-breaking bug), especially as I'm extremely busy with my other project and other things. Right now, I can only suggest looking into GPU scaling/aspect ratio options of your graphics card (maybe something like this could help?), so I apologize that I couldn't be of any more help!