@Smartik, honest question, why would that method be better? Not challenging at all, just looking for your insight mate
In my case, I pull the list of icons into my theme options and my page builder, so once an icon is chosen it's saved into an option, or into meta. So the array is only called in certain admin situations anyway and then the value saved by itself.
Because you don't have to update that list manually with every update of font awesome. In my example this will run everytime, but you can change it a bit and run it only when you want to update the list or write the array in a static file, or anything else.
It probably is not better, it is more flexible(that's what I should say), and allow to manipulate the code in many ways. Your code is excelent for what it is intended to do, but I've just added another solution that allows to get the code in an easy way.