It also feels like it's targeting the wrong thing. A far more common issue is "how do I split God Models into more manageable chunks". While something like @kaspth 's AssociatedObject feels a lot more natural and OO, there's a missing piece of infrastructure where you just move some related functions and constants into their own file and call it something like User::Authentication or Image::Sizing or whatever. No expectation of having to share it with other classes.