Formats tend to be tied in some strong nature to the way the engine works. Think of it this way: you could create your own engine, but then every difference bet

Formats tend to be tied in some strong nature to the way the engine works. Think of it this way: you could create your own engine, but then every difference between your engine and Unity is a bug from the artist's perspective (thing works correctly in Unity but does not in your engine). There's no sense in using the same format for your engine if you don't implement every single last checkbox and dropdown.