She can’t really reinterpret them... her voice will likely sound stronger and production might be clearer, but if she even slightly reinterprets or changes the songs in any way then there is no point to the whole thing as people who want to hear the original record will ultimately just keep going back to the originals. The point is that she wants anyone who wants to stream, say, You Belong With Me, to be just as satisfied choosing the re-recorded version. As we’ve seen, there is a lot of nostalgia when it comes to Taylor Swift, so even if she did some acoustic re-recording, in the end if there is that original sound that is what will have the most value... so that’s what she has to replicate.
The reason she is doing all these ‘vault’ songs is that people would get bored of just hearing literal re-records, especially of something like 1989 where it wasn’t that long ago. The vault songs make it seem like she’s offering something new, and she basically has to include ‘new’ material to keep attracting interest to what will ultimately be a rather mundane and arduous task— replicating songs and trying to sell them to the public.