Linking a file outside the Asset folder to update an asset on reimport

Hi all, Is there an option to change or extend the default behavior of Unity's editor to mirror Unreal Engine's Source File attribute for assets inside the project? When importing a file in Unreal, it keeps track of where the original file is, like on network storage. When you reimport the asset, it'll first check for a Source File value, and if one exists, it'll reimport from that file. In Unity, it only seems to look inside the Asset folder for changes, and reimporting just pulls the same file back in from the Asset folder. Is there a way to link to outside files so reimport will pull from a location other than inside the Asset folder? If not, is it possible to embed this into each asset (mostly just fbx's/textures/audio) and extend the behavior of reimport to check for this?

Thanks