Dario I remember that 'adventure'.
Last year I removed the battery and the 'tray' (more like a cage), cleaned it and then painted it with rustoleum. It is merely bolted to 2 studs coming down from the underside of the floor. I there is room for a real tray affair but I think the vertical cuts would have to go to the bottom of the exterior wall/skirting. I also don't think there is anything structural there, but the cutout piece would likely become a door. In fact, I STILL have to get those automatic battery fill things someone here told me about.