Fallout 1 is fine the way it is, Fallout 2 has its problems but if you go through changing everything at some point it stops being a remake. They both still work and they're $5. And both are owned by Interplay as of now anyway.
I don't see why turn based isometric Fallout can't at least coexist with the FPS ones, though.
Turn based is not "outdated" nor was it made obsolete by real-time combat. It's only as "dead" as people percieve it to be. There was a time when sidescrolling was considered "dead", now not only do we have Megaman 9, Sonic the Hedgehog 4, but we also have things like Braid.