I really hope that such a way of importing and replacing files will be supported one day. Just a semi-automatic way by adding two lists side-by-side, one with old content in library, and one with new files not yet imported, and the ability to drag and drop and a few more options would go a long way of simplifying todays replace operations very much.
I still have tons of albums that's in the process of being replaced, and this would make the job 1/3 of what it is now.