That sounds like a fantastic conversion of the John Deere 520 Flail Shredder (Mulcher) for FS25! The improvements you mentioned, such as editing the XML, textures, lighting, and effects, really help in bringing the model up to date and ensuring a more immersive gameplay experience for users. The fact that the mod passed the Giants Test Runner without any errors is a testament to the high quality of your work.
The addition of a 7.6m work area, adjustable rear wheel height, front rubber deflectors, heavy-duty gearbox, steel rotor bearings, and a square rotor design for superior strength really enhances the functionality and realism of the shredder in the game. The 100 hp requirement adds a layer of realism to the equipment, making players consider their choice of tractor for optimal performance.
Overall, it sounds like you've put a lot of effort into this mod, and I'm sure players will appreciate the attention to detail and functionality that you've added to the John Deere 520 Flail Shredder. Great job!